Tyrannosaurus rex Part 3: Taxonomy

As we already know, Tyrannosaurus rex was described in 1905 by Henry Fairfield Osborn (Osborn, 1905). Since then, Tyrannosaurus rex has gone through a great deal of change. Today we will look at some other dinosaurs that have, at one time or another, been regarded as the same as Tyrannosaurus rex.

1. Dynamosaurus imperiosus
The first of these synonyms is Dynamosaurus imperiosus (Imperial Powerful Lizard). This species was also described by Osborn (1905). Osborn distinguished Dynamosaurus based on the number and shape of the teeth and by the presence of dermal plates (in other words, armour), which would have been very exciting if that were true. However, after finding more material of both Tyrannosaurus and Dynamosaurus, Osborn realised they were the same thing (Osborn, 1906). Because Tyrannosaurus and Dynamosaurus were named at the same time, Osborn had the choice of which name to use and he went with Tyrannosaurus (in some alternate reality somewhere, Dynamosaurus is the most well-known dinosaur and Tyrannosaurus would be an obscure name known only to enthusiasts). The armour plating has subsequently been discovered to have come from an Ankylosaurus (Brown, 1908) by Kenneth Carpenter (2004).

2. Tarbosaurus bataar
The next major synonym is Tarbosaurus bataar (Warrior Alarming Lizard). This species was described by the Russian palaeontologist Evgeny Maleev in 1955 (Maleev, 1955a), who originally named it as a second species of Tyrannosaurus. Maleev distinguished bataar from rex by the number of teeth and the shape of its snout. Then, in 1965, another Russian palaeontologist, Anatoly Rozhdestvensky transferred the species to the genus Tarbosaurus (which was also named by Maleev (1955b)) (Rozhdestvensky, 1965). Since then, bataar has bounced from Tyrannosaurus to Tarbosaurus. Personally, I regard it as being separate from Tyrannosaurus rex but we'll look at this in more detail another day (it gets more complicated because Maleev already had a species within Tarbosaurus, Tarbosaurus efremovi, which is probably the same as bataar but maybe not).

3. Manospondylus gigas
OK, this is where things get complicated. Manospondylus gigas (Giant Porous Vertebra) was described by Edward Cope in 1892, initially as an 'agathaumid', which for our purposes is a ceratopsid (think Triceratops, etc.) (Cope, 1892). It is known only from two backbones. John Hatcher compared the backbones (of which he could only find one) to other dinosaurs from the same time and place. He noticed that the fossil was very similar to the vertebrae found in the theropod Dryptosaurus (Marsh, 1877). This convinced Hatcher that Manospondylus was a type of theropod and not a ceratopsian (Hatcher, 1907). Then, ten years later, Osborn made the observation that Cope's description and drawings of the specimen (which by this point had completely vanished) matched very well with Tyrannosaurus. However, due to the obscure nature of Manospondylus, Osborn refrained from synonymising the two. Then, nothing was heard about it until 2000 when new tyrannosaur material was discovered at Sioux Falls, South Dakota, the apparent locality where the Manospondylus fossils were discovered (the actual location is not known because Cope didn't include that information in his description but he did tell Hatcher about it before he wrote his paper). This new material included not only the dorsal vertebrae (backbones) but also ribs, jaw bones and parts of the skull. This material matched that of Manospondylus and also Tyrannosaurus (Anonymous, 2000). If this is accepted then we have a problem. Manospondylus predates Tyrannosaurus and therefore, technically, is the correct name. However, there is a rule within the ICZN (the list of conventions regarding animal names) that states that if the older name was published before 1899 and has not been regarded as a valid name in the 50 years after its original description in at least 25 publications by at least 10 authors, then the older name can be suppressed in favour of the younger name (Ride, 1999). Since Manospondylus fits this, as the only authors to mention it have been Hatcher and Osborn, Tyrannosaurus is safe for now (so long as the rules don't change).

4. Tyrannosaurus lancensis
Oh this guy. Tyrannosaurus lancensis (Tyrant Lizard from Lance), or Lance as I call him, has been, and continues to be, a headache. No-one can agree on what the specimen constitutes. It was originally described as a species of Gorgosaurus (Lambe, 1914) by Charles Gilmore (Gilmore, 1946). When Dale Russell synonymised Gorgosaurus with Albertosaurus (Osborn, 1905) he transferred lancensis over (Russell, 1970). Then in 1988, Robert Bakker, Michael Williams and Phil Currie gave Lance a new generic name: Nanotyrannus (Dwarf Tyrant) (Bakker et al., 1988). It was then considered a juvenile Tyrannosaurus rex by Thomas Carr (Carr, 1999). However, Currie still maintains lancensis is a distinct species from rex (though he is not sure if should be in a separate genus anymore) (Currie, 2003). So we now have three choices: regard it as being a juvenile Tyrannosaurus rex, a distinct species within Tyrannosaurus as Tyrannosaurus lancensis (which is what I have gone for) or treat it as a separate genus Nanotyrannus lancensis. Bakker, Currie and Greg Larson are supposedly working on a paper that will help to clarify the situation but as nothing has been heard about it since 2005 I suspect they've given up on it. Expect to hear more from Lance in the future.

5. Albertosaurus megagracilis
I don't know much about this one. The skeleton the species is based on, LACM 23845, was discovered in the Hell Creek Formation of Montana in 1967. It was initially believed to be a juvenile Tyrannosaurus rex. Then, in 1980, Ralph Molnar described the specimen as an individual of Albertosaurus lancensis (see above) (Molnar, 1980). Gregory Paul disagreed and named it as new species Albertosaurus "megagracilis" (Great Gracile Alberta Lizard) (Paul, 1988) (He only named it - he provided no description or any reason as to why it should be a distinct species - but palaeontologists still used the name). George Olshevsky placed the species in a new genus Dinotyrannus (Terrible Tyrant) (Olshevsky, 1995), using much of Molnar's original description. Finally, in 2004, Thomas Carr and Thomas Williamson re-examined the specimen and realised that Molnar had got a lot wrong, such as not recognising some features as being the result of damage, other features being entirely absent and misidentifying some bones. In their opinion, Dinotyrannus megagracilis was just a subadult Tyrannosaurus rex (Carr and Williamson, 2004) and everyone has agreed since.

6. Aublysodon molnari
This species has a similar story to megagracilis. The specimen, know as the Jordan Theropod was discovered in 1966 in the Hell Creek Formation of Montana and comprised a partial theropod snout. This was described by Ralph Molnar who thought it was a dromaeosaurid ("raptor") (Molnar, 1978). Next, Phil Currie disagreed and believed it was actually a tyrannosaur, probably within the genus Aublysodon (Backwards-Flowing Tooth) (Leidy, 1868, Currie, 1987). Gregory Paul went one step further and named it as a new species Aublysodon molnari (Molnar's Backwards-Flowing Tooth) (Paul, 1988) (Actually, he initially misspelled it as molnaris but he later corrected it (Paul, 1990)). However, Molnar and Kenneth Carpenter disagreed, instead believing it to be a specimen of Aublysodon mirandus (Leidy, 1868) because the teeth of the two species were identical (Molnar and Carpenter, 1989). Then George Olshevsky gave it its own generic name Stygivenator (Styx Hunter - the Styx was a river in the Greek Underworld and is a reference to the Hell Creek Formation) (Olshevsky, 1995). Stygivenator was said to be unique based on the narrowness of the snout and teeth. And everything was fine and dandy...but not for long! The two Toms (Carr and Williamson) were doubtful about its uniqueness and noted that it was very similar to a number of juvenile tyrannosaurs (Carr and Williamson, 2000). Then, another Tom, Thomas Holtz, regarded Stygivenator as being a close relative of another obscure tyrannosaur Alectrosaurus (Unmarried Lizard) (Gilmore, 1933, Holtz, 2001). Unfortunately, Alectrosaurus at that time was actually a chimaera, being composed of at least two different tyrannosaurs so this should be taken with a pinch of salt. Finally, Carr and Williamson (2004) showed that most of the unique characters of Stygivenator were either wrong or not unique, and that it in fact represented a juvenile Tyrannosaurus rex. Others have since agreed with that except Olshevsky.

7. Aublysodon amplus and Aublysodon cristatus
These two species were both described by Othniel Marsh in 1892 from the Lance Formation of Wyoming. Aublysodon amplus (Ample Backwards-Flowing Tooth) was based on teeth that had small serrations on their edges with narrow ridges at the rear. Aublysodon cristatus (Crested Backwards-Flowing Tooth) is also based on teeth which have no serrations and a sharp ridge at the rear (Marsh, 1892). Their small size and little to no serrations prompted Phil Currie to identify them as being juvenile tyrannosaur teeth (Currie, 2003) but juveniles of which tyrannosaur is the big question. Based on time and place they most likely belong to Tyrannosaurus rex but they are also indistinguishable from Daspletosaurus (Frightful Lizard) (Russell, 1970) and so their identity will remain unresolved.

And those are the all the synonyms of Tyrannosaurus rex. Next time will be the final part (I promise) looking at the biology of rex such as sexual dimorphism, posture, the role of the short arms etc. The next blog post, however, will take a brief look at the Mesozoic Era - the Age of the Dinosaurs.

See also:
More dinosaurs
Tyrannosaurus rex Part 4

References
Anonymous (2000), 'New Discovery may endanger T-Rex's name' [Online], url: http://www.iol.co.za/scitech/technology/new-discovery-may-endanger-t-rex-s-name-1.40212#.UlLJ29KbNHU, Accessed on: 07/09/2013

Bakker, R., Williams, M., and Currie, P. (1988) 'Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana', Hunteria, 1 (15), pp. 1-30

Brown, B. (1908) 'The Ankylosauridae, a new family of armored dinosaurs from the Upper Cretaceous', Bulletin of the American Museum of Natural History, 24, pp. 187-201

Carpenter, K. (2004) 'Redescription of Ankylosaurus magniventris Brown 1908 (Ankylosauridae) from the Upper Cretaceous of the Western Interior of North America', Canadian Journal of Earth Science, 41, pp. 961-986

Carr, T. (1999) 'Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Theropoda)', Journal of Vertebrate Paleontology, 19, pp. 497-520 

Carr, T. and Williamson, T. (2000) 'A review of Trannosauridae (Dinosauria: Coelurosauria) from New Mexico' in Lucas, S. and Heckert, A. (Eds) 'Dinosaurs of New Mexico', Bulletin of the New Mexico Museum of Natural History, 17, pp. 113-146

Carr, T. and Williamson, T. (2004) 'Diversity of late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from western North America', Zoological Journal of the Linnean Society, 142, pp. 479-523

Cope, E. (1892) 'Fourth note on the Dinosauria of the Laramie', American Naturalist, 26, pp. 756-758

Currie, P. (1987) 'Theropods of the Judith River Formation of Dinosaur Provincial Park', in Currie, P. and Koster, E. (Eds) Fourth Symposium on Mesozoic Terrestrial Ecosystems, Drumheller: Royal Tyrell Museum of Palaeontology

Currie, P. (2003) 'Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada', Acta Palaeontologica Polonica, 48 (2), pp. 191-226

Gilmore, C. (1933) 'On the dinosaurian fauna of the Iren Dabasu Formation' Bulletin of the American Museum of Natural History, 67, pp. 23-78

Gilmore, C. (1946) 'A new carnivorous dinosaur from the Lance Formation of Montana', Smithsonian Miscellaneous Collections, 106, pp. 1-19

Hatcher, J (1907) 'The Ceratopsia', U.S. Geological Society Monograph, 49, pp. 1-300

Holtz, T. (2001) 'Pedigree of the tyrant kings: New information on the origin and evolution of the Tyrannosauridae', Journal of Vertebrate Paleontology, 21 (3), pp. 62A-63A

Lambe, L. (1914) 'On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of the skull of Stephanosaurus marginatus from the same horizon', Ottawa Naturalist, 28, pp. 13-20

Leidy, J. (1868) 'Remarks on a jaw fragment of Megalosaurus', Proceedings of the Academy of Natural Sciences of Philadelphia, 20, pp. 197-200

Maleev, E. (1955a) 'Gigantic carnivorous dinosaurs of Mongolia', Doklady, Academy of Sciences, 104 (4), pp. 634-637

Maleev, E. (1955b) 'New carnivorous dinosaurs from the Upper Cretaceous of Mongolia], 104 (5), pp. 779-782

Marsh, O. (1877) 'Notice of some new dinosaurian reptiles from the Jurassic Formation', American Journal of Science, 3 (14), pp. 514-516

Marsh, O. (1892) 'Notes on Mesozoic vertebrate fossils', American Journal of Science, 44, pp. 756-758

Molnar, R. (1978) 'A new theropod Dinosaur from the Upper Cretaceous of Central Montana', Journal of Paleontology, 52 (1), pp. 73-82

Molnar, R. (1980) 'An albertosaur from the Hell Creek Formation of Montana' Journal of Paleontology, 54, pp. 102-108

Molnar, R. and Carpenter, K. (1989) 'The Jordan theropod (Maastrichtian, Montana, U.S.A.) referred to the genus Aublysodon', Geobios, 22, pp. 445-454

Olshevsky, G. (1995) 'The origin and evolution of the tyrannosaurids', Dinosaur Frontline, 9, pp. 92-119 and 10, pp. 75-99

Osborn, H. (1905) 'Tyrannosaurus and other Cretaceous carnivorous dinosaurs', Bulletin of the American Museum of Natural History, 21, pp. 259-265

Osborn, H. (1906) 'Tyrannosaurus, Upper Cretaceous carnivorous dinosaur', Bulletin of the American Museum of Natural History, 22, pp. 281-296

Paul, G. (1988) Predatory Dinosaurs of the World: A Complete Illustrated Guide, New York: Simon and Schuster

Paul, G. (1990) 'The many Myths, some old, some new, of Dinosaurology', Modern Geology, 16, pp. 69-99

Ride, W. (1999) 'Article 23.9 - Reversal of Precedence', International Code of Zoological Nomenclature, London: ICZN

Rozhdestvensky, A. (1965) 'Growth changes in Asian dinosaurs and some problems of their taxonomy', Paleontological Journal, 3, pp. 95-109

Russell, D. (1970) 'Tyrannosaurs from the Late Cretaceous of western Canada', National Museum of Natural Science Publications in Palaeontology, 1, pp. 1-34

Frequently Asked Dinosaur Question 2 and 3: How long did a dinosaur live and how fast did they grow?

(Massospondylus, Owen, 1854)

In regards to the first question, not much is known about how old individual dinosaurs lived for but estimates have been made. It is likely that dinosaurs did not have a long life-span. For example, the oldest known tyrannosaur was 28 and the oldest sauropod was 38 (Erickson et al., 2004). Reasons for such low life expectancies have been proposed as high predation on young individuals and fierce sexual competition for old (Erickson et al., 2006). These ages were based on growth rings on the dinosaur's bones.

(Triceratops, Marsh, 1889)

In regards to the second question, there has been a lot of research conducted on the growth rates of dinosaurs. Why? Because it can help to answer another question, namely were dinosaurs warm- or cold-blooded. This is based on the idea that warm-blooded or endothermic animals grow faster than cold-blooded or ectothermic ones. Dinosaurs were initially born in quite small eggs, with even the largest only being the size of a basketball (Carpenter et al., 1994). Through the numerous studies conducted in this area, it would appear that, compared to other reptiles, dinosaurs grew much faster. However, compared to mammals and birds, it is dependant on size. When comparing similarly sized animals, dinosaurs under 220 g grew slower than marsupials. Dinosaurs between 1-20 kg grew at the same rate as marsupials but slower than precocial birds (those able to run around from birth). Dinosaurs between 100-1000 kg grew faster than marsupials, at the same rate as precocial birds but slower than placental mammals. Dinosaurs between 1500-2500 kg grew at the same rate as most placental mammals (except whales) but slower than altricial birds (those that are born helpless). Finally, dinosaurs over 2500 kg grew faster than placental mammals, at the same rate as whales but still slower than altricial birds (if you scaled them up) (Erickson et al., 2001, Curry, 1999).

(Growth curves of four tyrannosaurids from Erickson et al., 2004)

Some studies have looked at individual dinosaurs. For example Erickson et al (2004) and Horner and Padian (2004) looked at Tyrannosaurus rex (Osborn, 1905). These studies showed that Tyrannosaurus exhibited a teenage growth spurt, just like human teenagers do. I wonder if Tyrannosaurus teenagers developed attitude problems as well? Anyway, I digress. Tyrannosaurus went from around half a ton at age ten to around five tons when they get to twenty. After that they practically stopped growing. However, some herbivorous dinosaurs could grow even faster. For example, the hadrosaur Hypacrosaurus (Brown, 1913) reached its full size of 9.1 m (Lull and Wright, 1942) and 4 tonnes (Horner et al., 2004) at the age of 15 (Cooper et al., 2008). This means (if my maths is correct), Hypacrosaurus grew, on average, 60 cm and 260 kgs a year.

 As can be seen then, dinosaurs lived relatively short lives but they grew very fast. This pattern is typical of warm-blooded animals. We'll look in more detail at this argument at a later date. Next will be the long awaited final part of Tyrannosaurus, looking at its taxonomy and any other interesting things I've missed out.

See also:
More dinosaurs
More about Tyrannosaurus rex

References
Brown, B. (1913) 'A new trachodont dinosaur, Hypacrosaurus, from the Edmonton Cretaceous of Alberta', Bulletin of the American Museum of Natural History, 32, pp. 395-406

Carpenter, K., Hirsch, K. and Horner, J. (1994) 'Introduction', in Carpenter, K., Hirsch, K. and Horner, J. (Eds) Dinosaur Eggs and Babies, Cambridge: Cambridge University Press

Cooper, L., Lee, A., Taper, M., and Horner, J. (2008) 'Relative growth rates of predator and prey dinosaurs reflect effects of predation', Proceedings of the Royal Society B, 275 (1651), pp. 2609-2615

Curry, K. (1999) 'Ontogenetic Histology of Apatosaurus (Dinosauria: Sauropoda): New Insights on Growth Rates and Longevity', Journal of Vertebrate Paleontology, 19 (4), pp. 654-665

Erickson, G., Rogers, K. and Yerby, S. (2001) 'Dinosaurian growth patterns and rapid avian growth rates', Nature, 412 (6845), pp. 429-433

Erickson, G., Makovicky, P., Currie, P., Norell, M., Yerby, S. and Brochu, C. (2004) 'Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs', Nature, 430 (7001), pp. 772-775

Erickson, G., Currie, P., Inouye, B. and Winn, A. (2006) 'Tyrannosaur Life Tables: An Example of Nonavian Dinosaur Population Biology', Science, 313 (5784), pp. 213-217

Horner, J. and Padian, K. (2004) 'Age and growth dynamics of Tyrannosaurus rex' Proceedings of the Royal Society B, 271 (1551), pp. 1875-1880

Horner, J., Weishampel, D. and Forster, C. (2004), 'Hadrosauridae', in Weishampel, D., Dodson, P. and Osmolska, H. (Eds) The Dinosauria (2nd Edition), Berkeley: University of California Press, pp. 438-463

Lull, R. and Wright, N. (1942) 'Hadrosaurian Dinosaurs of North America', Geological Society of America Special Papers, 40, pp. 1-242 

Marsh, O. (1889) 'Notice of gigantic horned Dinosauria from the Cretaceous', American Journal of Science, 3 (38), pp. 173-175

Osborn, H. (1905) 'Tyrannosaurus and other Cretaceous carnivorous dinosaurs', Bulletin of the American Museum of Natural History, 21, pp. 259-265

Owen, R. (1854) Descriptive Catalogue of the Fossil Organic Remains of Reptilia and Pices [sic] Contained in the Museum of the Royal Colleges of Surgeons of England, London: Taylor and Francis

Richard Owen (1804-1892): The Father of Dinosaurs

Richard Owen is one of the most important figures in the history of dinosaur research, primarily because he coined the term "dinosaur" and realised they were not just big lizards as previously believed but an entirely new group of reptiles. But despite this, he was not a very popular man amongst his colleagues. Let's take a closer look.

Owen was born on 20 July 1804 in Lancaster. He had five siblings. His father, also named Richard, was a merchant based in the West Indies. His mother, Catherine Parrin, was a Hughenot (a French protestant). Owen went to Lancaster Royal Grammar School (which today is a specialist Technology and Language college). He became an apprentice to a local surgeon and apothecary in 1820 where he gained sufficient medical knowledge to enrol as a medical student at Edinburgh University in 1824. The following year, he left the university to complete his medical training at St. Bartholomew's Hospital, London, where he was greatly influenced by the surgeon John Abernethy (nicknamed "Dr. My-Book" because of the number of times he referred to his book when dealing with patients).

 In July 1835, Richard married Caroline Clift in St. Pancras and the couple had one son, William. After he had completed his education, Owen intended to pursue anatomical research. However, Abernethy persuaded Owen to become the assistant to William Clift, the conservator of the Royal College of Surgeons. In this way, Owen changed his mind, and instead chose to become a scientific researcher. His first endeavour was to produce a catalogue of the specimens in the Hunterian Collection in the Royal College of Surgeons. This gave him the knowledge and experience necessary for him to become one the greatest biologists of his time.

Owen became a professor in 1836 and subsequently, in 1849, succeeded Clift as conservator. He remained in this position until 1856 when he became superintendent of the natural history collection of the British Museum. It was here that he made his greatest contribution to science, as he campaigned long and hard for the collection to be moved to a new building. This was eventually achieved in 1883 when the Natural History Museum in South Kensington, London was built. In reward for this accomplishment, Owen received a knighthood. Unfortunately, throughout his career, Owen was often accused of not properly acknowledging others for their work or taking credit for others' discoveries. This was most apparent in 1846 when he wrote a paper on belemnites (fossil molluscs similar to squid) but did not give credit to Chaning Pearce who had already described belemnites in 1842. As a result of this, Owen was struck off the councils of the Royal Society and the Zoological Society.

(Nautilus pompilius (Linnaeus, 1758))

Whilst Owen was busy describing the specimens in the Hunterian collection, he also dissected and described specimens that had recently died at London Zoo. His first major paper, and the one that brought him attention from other scientists, was his Memoir on the Pearly Nautilus (Owen, 1832). Amongst his other contributions to invertebrate science was his description of the Venus' Flower-Basket Sponge, Euplectella aspergillum (Owen, 1841), the roundworm Trichinella spiralis (Owen, 1835), he gave the Ram's Horn Squid (Spirula spirula, (Linnaeus, 1758)) its own family Spirulidae (Owen, 1836) and he described the oldest fossil footprints Protichnites (Owen, 1852) which he believed were produced by an animal similar to a horseshoe crab.

Despite his advances in invertebrate research, it was through studying vertebrates that Owen really excelled. His book Comparative Anatomy and Physiology of Vertebrates, published in three volumes between 1866 and 1868, served as the most authoritative source of anatomical information for vertebrates in the late 19th century. He also wrote extensively on teeth, culminating in the book Odontography in 1840. His greatest contribution to fish was his description of the African Lungfish genus Protopterus (Owen, 1839a).

 For the reptiles, Owen wrote a series of books entitled History of British Fossil Reptiles, published in four volumes between 1849 and 1884. His best-known contribution was his description of Dinosauria (Owen, 1842) which he based on three known dinosaurs: Megalosaurus (Buckland, 1824), Iguanodon (Mantell, 1825) and Hylaeosaurus (Mantell, 1833). Other fossil dinosaurs were known but they were believed to be large lizards or crocodiles and were not recognised as dinosaurs until much later. He also discovered a group of fossil reptiles that had similarities with both reptiles and mammals which he named Anomodontia (Owen, 1859a) which started with his description of Dicynodon (Owen, 1845). 

 For birds, he wrote papers on kiwis, dodos and other flightless birds, but his best known paper was one on Archaeopteryx (Meyer, 1861) in 1863 (Owen, 1863). 

 But perhaps Owen's greatest contribution to vertebrate research is his collaboration with Benjamin Waterhouse Hawkins with whom he constructed the prehistoric models in the Crystal Palace Gardens, which can still be seen today.

(Owen's depiction of a camel)

Finally, we arrive at his mammalian contributions. Firstly, he split the hoofed mammals into two orders: Artiodactyla (Owen, 1848) and Perissodactyla (Owen, 1848). Artiodactyla contains the even-toed hoofed mammals such as cattle, sheep, goats, deer, giraffes, pigs and hippopotamus. Perissodactyla contains the odd-toed hoofed mammals such as horses, tapirs and rhinoceros. Charles Darwin, whom Owen would have a rocky relationship with due to his theory of Evolution, collected a series of fossils of large hoofed mammal from South America which Owen described as Toxodon (Owen, 1837). Toxodon defied every attempt to classify it because it had similarties with hoofed mammals, rodents and whales, lending credence to Darwin's ideas. Owen continued to study the strange South American fossil mammals and described the giant armadillo Glyptodon (Owen, 1839b) and the giant ground sloth Mylodon (Owen, 1840). 

 Meanwhile, another explorer, Sir Thomas Mitchell, donated some giant fossil bones he had found in Australia to Owen. From these, Owen described Diprotodon (Owen, 1838), a giant wombat and Thylacoleo (Owen, 1859b) a carnivorous marsupial.

(Owen with a moa skeleton)

Now we come to the darker side of Owen. Owen had many feuds with many other scientists, most of which were vicious. His best known rivalry was with Charles Darwin who proposed the Theory of Evolution through Natural Selection. Owen initially believed that while species were effectively unchangeable and fixed, God modified pre-existing forms to produce new species. This is why animals look similar to each other. However, by the 1840s, Owen had changed his mind and came to believe that species arose from an evolutionary process as evidenced by his claim in 1849 that humans ultimately descended from fish (Richards, 1987). For this, he was heavily criticised and ridiculed and this likely stopped him from elaborating on his theories in his later career. However, he strongly disagreed with Darwin about man descending from apes. Owen went to great lengths to prove that humans could not have evolved from apes such as suggesting that apes lacked certain structures in their brain and their brains were far too small (Cosans, 2009).
 In response, Thomas Huxley (nicknamed Darwin's bulldog because of his aggressive defence of Darwin's theories) argued that a gorilla's brain is as similar to a baboon's as it is to a human's. Owen largely kept quiet in the face of this criticism...publicly that is. In 1860, Owen published an anonymous review of Darwin's On the Origin of Species (Owen, 1860). In it, Owen not only ridiculed and criticised Darwin's ideas, he also labelled Huxley and Joseph Hooker as short-sighted for defending Darwin so vigorously and even went so far as to say that On the Origin of Species symbolised an "abuse of science... to which a neighbouring nation, some seventy years since, owed its temporary degradation" referring to the French Revolution. In other words, if science accepts Darwin's theories, society will descend into the same chaos and anarchy as France seventy years earlier. Pretty dramatic.
 Huxley countered by presenting public dissections of various apes and visibly demonstrating the structures that Owen said didn't exist. Owen responded by admitting that there may be unique individuals with very poorly developed brain structures but ape brains are still far too small to be the ancestors of humans. Then it turned uglier. Huxley countered that due to "racial differences", man's brain size varies considerably with European man having larger brains and African man having smaller, ape-like brains (Huxley, 1861). Owen, however, downplayed these differences, remarking that brain size does not differ dramatically across the races. Owen and Huxley continued to fight for the rest of their lives. The scientific community largely sided with Darwin and Huxley. But Owen's anti-Darwinist views weren't the only reason why he was unpopular.
 As well as Darwin and Huxley, Owen had a lengthy feud with Gideon Mantell, in particular about the discovery of Iguanodon. Owen credited himself and Georges Cuvier with Iguanodon. When the scientific community sided with Mantell (Cuvier didn't really care much who received the credit), Owen became bitter. When he was president of the Royal Society, he used his influence to prevent many of Mantell's papers from being published. When Mantell suffered his horrible carriage accident that left him crippled and addicted to painkillers, Owen attempted to re-name many of Mantell's dinosaurs and even tried to claim he discovered them and not Mantell. His personal animosity towards Mantell and his previously mentioned Belemnite scandal with Pearce caused him to be removed from many academic institutions.

 After the British Museum of Natural History had been built and the collections transferred in 1883, Owen retired from academics and lived out the rest of his life at Sheen Cottage in Richmond Park until his death in 1892. Sheen Cottage was destroyed by German bombs in 1944 but the remains of the outer walls can still be seen.

The next biography will look at another controversial palaeontologist with a famous rivalry, the American Edward Drinker Cope. The next post, however, will look at another frequently asked question: How long did dinosaurs live for?

See also:
More dinosaurs
What is a dinosaur?
Gideon Mantell

References

Buckland, W. (1824) 'Notice on the Megalosaurus or great Fossil Lizard of Stonesfield', Transactions of the Geological Society of London, 2 (1), pp. 390-396

Cosans, C. (2009) Owen's Ape & Darwin's Bulldog: Beyond Darwinism and Creationism, Bloomington: Indiana University Press

Huxley, T. (1861) 'On the Zoological Relations of Man with the Lower Animals', Natural History Review, 1, pp. 67-84

Mantell, G. (1825) 'Notice on the Iguanodon, a newly discovered fossil reptile, from the sandstone of Tilgate forest, in Sussex', Philosophical Transactions of the Royal Society, 115, pp. 179-186

Mantell, G. (1833) The Geology of the South-East of England, London: Longman Ltd

Meyer, H. von (1861) 'Archaeopteryx lithographica (Vogel-Feder) und Pterodactylus von Solenhofen' Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefakten-Kunde, pp. 678-679

Richards, E. (1987) 'A Question of Property Rights: Richard Owen's Evolutionism Reassessed', British Journal of the History of Science, 20, pp. 129-171

Owen, R. (1832) Memoir on the Pearly Nautilus (Nautilus pompilius, Linné). With illustrations of its external and internal structure, London: R. Taylor

Owen, R. (1835) 'Description of a microscopic entozoon infesting the muscles of the human body', Transactions of the Zoological Society of London, 1 (4), pp. 315-324

Owen, R. (1836) 'Descriptions of some new or rare Cephalopoda, collected by Mr. George Bennett, Corr. Memb. Z. S.', Proceedings of the Zoological Society of London, 37, pp. 19-24

Owen, R. (1837) 'A description of the Cranium of the Toxodon Platensis, a gigantic extinct mammiferous species, referrible by its dentition to the Rodentia, but with affinities to the Pachydermata and the Herbivorous Cetacea', Proceedings of the Geological Society of London, 2, pp. 541-542

Owen, R. (1838) 'Fossil remains from Wellington Valley, Australia. Marsupialia' in Mitchell, T. (Ed) Three Expeditions into the Interior of Eastern Australia, with Descriptions of the Recently Explored Region of Australia Felix, and of the Present Colony of New South Wales, London: T. and W. Boone

Owen, R. (1839a) 'On a new species of the genus Lepidosiren of Fitzinger and Natterer', Proceedings of the Zoological Society of London, 1, pp. 327-361

Owen, R. (1839b) 'Description of a tooth and part of the skeleton of the Glyptodon, a large quadruped of the edentate order, to which belongs the tessellated bony armour figured by Mr. CLIFT in his memoir on the remains of the Megatherium, brought to England by Sir WOODBINE PARISH, F.G.S.', Proceedings of the Geological Society of London, 3, pp. 108-113

Owen, R. (1840) 'Description of a mutilated lower jaw and teeth, on which is founded a subgenus of megatherioid edentata, under the name of Mylodon', The Zoology of the Voyage of H.M.S. Beagle, under the command of Captain Fitzroy, R.N., during the years 1832 to 1836, pp. 63-73

Owen, R. (1841) 'On a new genus and species of sponge (Euplectella aspergillum)', Transactions of the Zoological Society of London, 3 (2), pp. 203-206

Owen, R. (1842) Report of British Fossil Reptiles Part II, London: John Murray

Owen, R. (1845) 'Report on the Reptilian Fossils of South Africa - Part I: Description of certain Fossil Crania, discovered by A. G. Bain, Esq., in Sandstone Rocks at the South-eastern extremity of Africa, referable to different species of an Extinct genus of Reptilia (Dicynodon), and indicative of a new Tribe or Sub-order of Sauria', Transactions of the Geological Society of London, 2 (7), pp. 59-84

Owen, R. (1848) 'Description of teeth and portions of jaws of two extinct anthracotherioid quadrupeds (Hyopotamus vectianus and Hyop. bovinus) discovered by the Marchioness of Hastings in the Eocene deposits on the N.W. coast of the Isle of Wight: with an attempt to develop Cuvier's idea of the classification of pachyderms by the number of their toes', Quarterly Journal of the Geological Society of London, 4, pp. 103-141

Owen, R. (1852) 'Description of the impressions and footprints of the Protichnites from the Potsdam sandstone of Canada' Geological Society of London Quarterly Journal, 8, pp. 214-225

Owen, R. (1859a) 'On the orders of fossil and recent Reptilia, and their distribution in time', Report of the British Association for the Advancement of Science, 29 (1), pp. 153-166

Owen, R. (1859b) 'On the fossil mammals of Australia. Part II. Description of a mutilated skull of the large marsupial carnivore (Thylacoleo carnifex Owen), from a calcareous conglomerate stratum, eighty miles S. W. of Melbourne, Victoria', Philosophical Transactions of the Royal Society, 149, pp. 309-322

Owen, R. (1860) 'Darwin on the Origin of Species', Edinburgh Review, 3, pp. 487-532

Owen, R. (1863) 'On the Archaeopteryx of Von Meyer, with a description of the fossil remains of a long-tailed species from the lithographic stone of Solnhofen' Philosophical Transactions of the Royal Society, 153, pp. 33-47

Linnaeus, C. (1758) Systema naturae per regna tria naturae: secundum classes, ordines, genera, species, cum characteribus, differentiis, synonomis, locis (10th Edition), Stockholm: Laurentius Salvius

Discovering a dinosaur

Discovering a fossil is a wonderful experience and palaeontologists become really excited when they go on a fossil-hunting expedition (which doesn't happen that often - usually they stay at home, in a stuffy lab, studying fossils that are kept in the storage room of a museum). And their expeditions normally start when a member of the public finds an unusual specimen and alerts the experts. But before you go gallivanting across the countryside attempting to find the "next big thing", you need to know what it is you are looking for.

As can be seen in the above picture, there are usually large teams involved in digging up a dinosaur. This is because there is A LOT of work that needs to be done. You need people to dig large amounts of earth and rock (sometimes done with a machine if the fossil is deep enough), others need to remove small amounts of rock surrounding the fossil. You need a photographer to take pictures of the fossil and the surrounding area so researchers have a better idea of the rocks and the orientation of the fossil. And you need people to prepare the specimens for transport - this normally involves coating bones in plaster of paris and labelling them. In short, this isn't for people who prefer to work alone. You need people who know what they're doing.

(Grand Canyon, Arizona)

So, let's just say you are a palaeontologist and someone has presented you with a very impressive fossil. You have recruited all the relevant team members and you have arrived at the site. What's next? You need to know which rocks are more likely to harbour fossils than others. The best rocks for that are sedimentary rocks such as sandstones, mudstones, shales and limestones. Sometimes metamorphic rocks (rocks that have been shaped by intense heat and pressure such as slate) can contain fossils but they are often very distorted. Cliffs are really good places and it helps if they're by the sea because the water and wind will erode the outer layers of rock and expose the fossils underneath. This is why palaeontologists get really excited about a rockslide on the beach.

Unfortunately, many of the locations where fossils are found are very dangerous. As mentioned, they are normally found in areas prone to landslides and other effects of erosion and weathering. And though I've never tried it, I'm pretty sure the human body does like being thrown off steep cliffs. There is also an additional danger. Sometimes the land that fossils are found in are private and most people don't appreciate trespassers, especially if they are digging large holes everywhere. So remember, stay safe and always ask permission before you do anything. 

So they are my tips: gather a large team, look for sedimentary rocks, stay away from danger and obtain permission from any landowners. Next time, we'll look at what happens to the fossils when they get back to the museum or lab. In the next post, we'll look further into the man that gave us dinosaurs: Richard Owen

Heads up!

Dinosaurs are strange looking things aren't they? They resemble nothing that exists today. However, if we look closer, we can spot some similarities between them and living animals. In this post, we'll take a look a their skulls - what do they tell us about how dinosaurs lived?

First up is Prenocephale (Preen-o-sef-a-lee) (Sloped Head) (Maryanska and Osmolska, 1974). As can be seen in the picture, Prenocephale possesses a domed head. The function of the dome is a matter of much debate with ideas ranging from competition between males for mating (Colbert, 1955) to species or individual recognition (Goodwin and Horner, 2004).

Next is Troodon (Tro-o-don) (Wounding Tooth) (Leidy, 1856). The narrow, delicate jaw it possesses would indicate it is a carnivore. It has large, forward-facing eyes that helped it to gauge distances when hunting for prey. It's teeth, however, tells a more complicated story. To keep it short, there are two opposing views. That of Holtz et al. (1998), who believe Troodon to be omnivorous (based on the size and spacing of its denticles (small serrations on the tooth itself)) and Fiorillo (2008), who believes them to be entirely carnivorous (based on the large size of the teeth and their wear patterns). Now, you may have heard that Troodon is the most intelligent dinosaur based on its brain-to-body size ratio. We'll be looking at this claim in more detail later.

Next is Euoplocephalus (Yoo-Op-Low-Seff-A-Lus) (Well Armoured Head) (Lambe, 1910). Euoplocephalus has a wedge-shaped, squat head protected by spikes. It also has a short, wide mouth similar to a rhinoceros' with which it ate low-growing plants and shrubs. It's skull is very distinctive when compared to other ankylosaurs with relatively small, variably fluted teeth that lack a cingulum (a ridge at the base of the tooth), modified palpebrals (eyelids), shallow nostrils and the teeth of the upper jaw are curved towards the middle (Vickaryous and Russell, 2003). It also possessed bony eyelids, however, these are no longer regarded as being unique to Euoplocephalus (Coombs, 1972). However, despite this slew of defining characteristics it has recently been suggested that what we know of as Euoplocephalus is actually composed of four different genera namely: Euoplocephalus, Anodontosaurus (An-Oh-Dont-Oh-Saw-Us) (Toothless Lizard) (Sternberg, 1929), Scolosaurus (Sko-Low-Saw-Us) (Pointed Stake Lizard) (Nopcsa, 1928) and Dyoplosaurus (Die-Op-Low-Saw-Us) (Doubly-Armoured Lizard) (Parks, 1924). If this is the case, the distinguishing features of Euoplocephalus would become: absence of any ornamentation behind the eyes and, on the first armour ring of the neck, again no ornamentation and the osteoderms (bony scales) in the middle have a keel (in biology, ornamention is anything that serves as a display feature like spikes, horns, brightly-coloured feathers etc.) (Arbour and Currie, 2013). But we'll look in more detail on that later.

Finally, we have Styracosaurus (Stye-Rack-Oh-Saw-Us) (Spiked Lizard) (Lambe, 1913). Pretty impressive skull isn't it? There is a lot of variation amongst Styracosaurus individuals but they all seem to have had at least four large spikes on the frill. These spines could reach 50-55 cm long (Dodson, 1996). The large nasal horn, however, is probably not as big as depicted in this picture. The original specimen that Lambe used to described Styracosaurus had an incomplete horn. Lambe estimated that this horn was about 57 cm long. However, based on other material discovered since, the horn probably probably ended in a rounded tip about 20 cm long (Ryan et al., 2007). The function of the frill and horns has been debated about for decades. The ideas have been: attachment points for large jaw muscles (Lull, 1908); combat/defence (Farke et al., 2009); to regulate body temperature in a similar fashion to elephant's ears (Wheeler, 1978); and for sexual display (Farlow and Dodson, 1975).

So, as can be seen, dinosaur skulls are very varied and can provide us with a lot of information, even if there are still many unanswered questions. Next time, we'll take a look at another four dinosaur skulls. However, for the next post, we'll look at the process palaeontologists take to find, excavate and study fossils, starting with where they look for fossils.

See also:
More dinosaurs
More dinosaur anatomy
Even more dinosaur anatomy

References

Arbour, V. and Currie, P. (2013) 'Euoplocephalus tutus and the Diversity of Ankylosaurid Dinosaurs in the Late Cretaceous of Alberta, Canada, and Montana, USA', PLoS One, http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062421

Colbert, E. (1955) Evolution of the Vertebrates, New York: John Wiley

Coombs, W. (1972) 'The Bony Eyelid of Euoplocephalus (Reptilia, Ornithischia)', Journal of Paleontology, 46 (5), pp. 637-650

Dodson, P. (1996) The Horned Dinosaurs: A Natural History, Princeton: Princeton University Press

Farke, A., Wolf, E., Tanke, D. and Sereno, P. (2009) 'Evidence of combat in Triceratops', PLoS One, http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0004252

Farlow, J. and Dodson, P. (1975) 'The behavioral significance of frill and horn morphology in ceratopsian dinosaurs', Evolution, 29 (2), pp. 353-361

Fiorillo, A. (2008) 'On the Occurrence of Exceptionally Large Teeth of Troodon (Dinosauria: Saurischia) from the Late Cretaceous of Northern Alaska', Palaios, 23 (5), pp. 322-328

Goodwin, M. and Horner, J. (2004) 'Cranial histology of pachycephalosaurs (Ornithischia: Marginocephalia) reveals transitory structures inconsistent with head-butting behavior', Paleobiology, 30 (2), pp. 253-267

Holtz, T., Brinkman, D. and Chandler, C. (1998) 'Denticle morphometrics and a possibly omnivorous feeding habit for the theropod dinosaur Troodon', Gaia, 15, pp. 159-166

Lambe, L. (1910) 'Note on the parietal crest of Centrosaurus apertus, and a proprosed new generic name for Stereocephalus tutus' Ottawa Naturalist, 24, pp. 149-151

Lambe, L. (1913) 'A new genus and species of Ceratopsia from the Belly River Formation of Alberta', Ottawa Naturalist, 27, pp. 109-116

Leidy, J. (1856) 'Notice of remains of extinct reptiles and fishes, discovered by Dr. F. V. Hayden in the badlands of the Judith River, Nebraska Territory', Proceedings of the Academy of Natural Sciences of Philadelphia, 8, pp. 72-73

Lull, R. (1908) 'The cranial musculature and the origin of the frill in the ceratopsian dinosaurs', American Journal of Science, 4 (25), pp. 387-399

Maryanska, T. and Osmolska, H. (1974) 'Pachycephalosauria, a new sub-order of ornithischian dinosaurs', Paleontologia Polonica, 30 (3), pp. 45-102

Nopcsa, F. (1928) 'Dinosaurierreste aus Siebenbuergen' Geological Hungarica Series Palaeontologica, 4, pp. 1-76

Parks, W. (1924) 'Dyoplosaurus acutosquameus, a new genus and species of armored dinosaur; with notes on a skeleton of Prosaurolophus maximus', University of Toronto Studies Geological Series, 18, pp. 1-35

Ryan, M., Holmes, R. and Russell, A. (2007) 'A revision of the late Campanian centrosaurine ceratopsid genus Styracosaurus from the Western Interior of North America', Journal of Vertebrate Paleontology, 27 (4), pp. 944-962

Sternberg, C. (1929) 'A toothless armored dinosaur from the Upper Cretaceous of Alberta', Bulletin of the National Museum of Canada, 54 (49), pp. 28-33

Vickaryous, M. and Russell, A. (2003) 'A redescription of the skull of Euoplocephalus tutus (Archosauria: Ornithischia): a foundation for comparative and systematic studies of ankylosaurian dinosaurs', Zoological Journal of the Linnean Society, 137 (1), pp. 157-186

Wheeler, P. (1978) 'Elaborate CNS cooling structures in large dinosaurs' Nature, 275 (5679), pp. 441-443

Jurassic Park Part 2 - Were the raptors wrong?

In the last JP post, I examined the possibility of cloning a dinosaur. While that is a hypothetical and somewhat fanciful idea, it at least gets people, average Joe Bloggs and scientists alike, to discuss interesting ideas. However, there are other issues raised by the movies that have not resulted in such civil conversations. Today, we'll look at the main controversies surrounding the raptors (or, to use their proper name the Dromaeosaurids): their identity, size, presence of feathers, intelligence and their wrist positions.

(Velociraptor)

Officially, the raptors that appear in the various Jurassic Park media are Velociraptor (Osborn, 1924). However, at the time the movie was being made, there was a view that Velociraptor was the same genus as its much larger, North American cousin Deinonychus (Ostrom, 1969; Paul, 1988), leading some to believe the raptors are actually Deinonychus, further explaining why Dr. Grant identifies the fossil at the beginning of the movie as Velociraptor, despite being in the US (Velociraptor is from Mongolia). Others on the internet, believe that because the raptors in the movie are still too big to be Deinonychus (we'll be looking at size later), they could very well be based on Deinonychus' larger relative Achillobator (Perle et al., 1999) (although being named in 1999, the fossil was known since 1989). The fourth, and in my opinion least likely, interpretation, is that they are of Utahraptor (Kirkland et al., 1993). I personally believe that they were large Deinonychus (in disguise as Velociraptor).

(Deinonychus)

The next issue, and the one that gets argued about the most, is how big the raptors were. The raptors in the movie are depicted as being 3-4 m long and about 2 m high. Comparing this with the four candidates, Velociraptor was 2.07 m long and 50 cm high at the hip (Paul, 1988). Clearly, it is much too small. Deinonychus was a bit bigger, being 3.4 m long and 87 cm high at the hip (Paul, 1988). Closer to the JP raptors, but still being a bit small. Achillobator was bigger still, being nearly 6 m long (Holtz, 2010), nearly twice the size of the raptors in JP. Finally, Utahraptor was a true giant, measuring at least 7 m long (Kirkland et al., 1993) and with some potential specimens being 11 m long (Britt et al., 2001) - nearly 3 times the size of the JP raptors! (now you see why I consider Utahraptor to be very unlikely). Based on size, a large Deinonychus is the most likely.

(Achillobator)

In Jurassic Park III, the raptors are depicted as having feathers. Were the film-makers right and, if so, why don't the raptors in JP1 & 2 have feathers? The first evidence that Velociraptor had feathers came in 2007 in the form of little pits found in the forearm of a Velociraptor skeleton. These were interpreted as being attachment points for feathers (Turner et al., 2007). While this discovery was made 6 years after JP3, at the time, a number of Velociraptor's relatives were known to be feathered and therefore it was pretty likely Velociraptor was as well. In contrast, when JP1 & 2 were being made, only a small handful of dinosaurs were believed to be feathered and most of them were only tenuous suggestions with the first definite feather remains being discovered in 1996 (Sinosauropteryx, (Ji and Ji, 1996)), the year before JP2. Therefore, the movies reflect the current scientific opinions of the time.

(Utahraptor)

The next issue is also one that highlights the differences between JP3 and JP1 & 2. In JP3 the raptors are depicted as being highly intelligent, even being able to set traps. In contrast, the raptors from JP1 & 2 were more bestial and instinctive. So which version is the more accurate one? The problem with intelligence, is that there is no reliable way of measuring it. But given that raptors are closely related to birds, they probably were quite intelligent, though not as intelligent as depicted in JP3, however.

(Sinosauropteryx)

The final issue I want to address is something that a lot of non-technical works get wrong. Whenever theropods are depicted in movies or documentaries, they are nearly always shown with their hands facing downwards or towards the body. This, however, is wrong. In fact, their hands would have faced each other because theropods lacked the muscles in their forearms that would enable them to rotate their hands. Additional evidence for this comes from an Early Jurassic resting trace from Utah in which the hand prints were preserved leaning on their side rather than on their palms (Milner et al., 2009).

Overall, I think we can all agree that the raptors in Jurassic Park are not completely accurate. But then again, it wasn't the film makers' intention to create a genuine experience. They just wanted to make an entertaining movie and hell of a lot of money (which they succeeded at). Therefore, I think the best way to proceed is to be content with the idea that while the raptors were based on various Dromaeosaurids, they are an entirely fictional entity. My next JP post will look at the Dilophosaurus, which causes even more arguments than the raptors do. Next time, we'll take a closer look at the anatomy of various dinosaurs, starting with their heads.

See also:
More dinosaurs
More Jurassic Park

References
Britt, B., Chure, D., Stadtman, K., Madsen, J., Scheetz, R. and Burge, D. (2001) 'New osteological data and the affinities of Utahraptor from the Cedar Mountain Fm (Early Cretaceous of Utah)', Journal of Vertebrate Paleontology, 21 (3), p. 36A

Holtz, T. (2010) Dinosaurs: The Most Complete Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, New York: Random House

Kirkland, J., Burge, D. and Gaston, R. (1993) 'A large dromaeosaur (Theropoda) from the Lower Cretaceous of eastern Utah', Hunteria, 2 (10), pp. 1-16

Milner, A., Harris, J., Lockley, M., Kirkland, J. and Matthews, N. (2009) 'Bird-like Anatomy, Posture and Behavior Revealed by an Early Jurassic Theropod Dinosaur Resting Trace', PLoS One, http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0004591

Ji, Q. and Ji, S. (1996) 'On discovery of the earliest bird fossil in China and the origin of birds', Chinese Geology, 10 (233), pp. 30-33

Osborn, H. (1924) 'Three new Theropoda, Protoceratops zone, central Mongolia', American Museum Novitates, 144, p. 1-12

Ostrom, J. (1969) 'Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana', Bulletin of the Peabody Museum of Natural History, 30, pp. 1-165

Paul, G. (1988) Predatory Dinosaurs of the World: A Complete Illustrated Guide, New York: Simon & Schuster

Perle, A., Norell, M. and Clark, J. (1999) 'A new maniraptoran theropod - Achillobator giganticus (Dromaeosauridae) - from the Upper Cretaceous of Burkhant, Mongolia', Contributions of the Mongolian-American Paleontological Project,, 101, p. 1-105

Turner, A., Makovicky, P. and Norell, M. (2007) 'Feather Quill Knobs in the Dinosaur Velociraptor', Science, 317 (5845), p. 1721

Life before dinosaurs

(The diverse range of life during the Cambrian 541-485 million years ago)

You may be forgiven for believing that dinosaurs were the earliest animals to appear. After all, when was the last time you heard such famous names as Dimetrodon (Cope, 1878), Ichthyostega (Save-Soderbergh, 1932) or Vinlandostrophia (Zuykov and Harper, 2007), all of which predate dinosaurs by a considerable amount of time. In this article, we will look at the major steps life took to get from the earliest, simplest forms of life to becoming a dinosaur.

(Stromatolite colonies at Shark Bay, Australia)

The oldest fossils found have been dated to about 3.4 billion years ago, single-celled organisms that used sulphur rather than oxygen (Wacey et al., 2011) (we'll be looking at the origin of life and the origin of Earth another day). Such organisms are still around today. They are called cyanobacteria and are found in anaerobic (oxygen-less) environments, the most famous examples being stromatolites.

(Life in the Pre-Cambrian)

Towards the end of the Pre-Cambrian, about 635-542 million years ago, the first true multicellular lifeforms appeared. They are called the Ediacara biota, after the Ediacara Hills, Australia where many fossils have been found (Termier and Termier, 1960). Most of them just look like blobs of jelly, and indeed, many of them are still not universally accepted as being fossils. Along with this, their identity and where they fit into the tree of life, has remained a topic of much debate. Ideas have included: cnidarians (jellyfish, sea anemones, corals etc.) (Donovan and Lewis, 2001), the universal ancestors of all the animals (Glaessner, 1984), completely different forms of life that no longer exist (Seilacher, 1984), lichens (Retallack, 1994), algae (Ford, 1958), amoebae (Zhuravlev, 1992), fungi (Peterson et al., 2003) or bacterial colonies (Grazhdankin, 2001). Whatever they were, we'll be looking at them in more detail at a later date.

(Jellyfish Chrysaora fuscescens (Brandt, 1835))

At the start of the Cambrian, around 542 million years ago, something strange happened. The previous Ediacaran fauna, consisting of blob-things, largely disappeared (some persisting as late as the Mid Cambrian (Conway Morris, 1993)) and were replaced by organisms with hard parts (such as bone, teeth, shells etc.) and that resembled modern organisms such as jellyfish, molluscs and even vertebrates. This has been termed the "Cambrian Explosion of Life". But what happened? Where did these gribblies come from? And where did the Ediacaran "animals" go? These questions will be investigated some other day.

(Cooksonia (Lang, 1937), an early land plant)

The next major step for life was the colonisation of land. The earliest evidence for terrestrial life is found in rocks about 490 million years old. These fossils are of footprints believed to have been left by a strange group of amphibious arthropods called euthycarcinoids, which are regarded as being closely related to the myriapods (centipedes, millipedes and some other groups of long, multi-legged arthropods) (MacNaughton et al., 2002). Plants first appeared on land during the Mid Ordovician, around 476 million years ago. The evidence for this is based on spores of land plants similar to liverworts. The earliest definite land plant fossils are from 430 million-year-old rocks and belonged to a group called the club-mosses (Kenrick and Crane, 1997).

(Helicoprion, (Karpinsky, 1899), an early shark-like fish)

The ancestors of the fish probably appeared about 530 million years ago and resembled short, fat eels (Shu et al., 1999). These first fish were jawless like today's lampreys and hagfish. Later, around 500-430 million years ago, large armoured jawless fish, called ostracoderms, appeared. Not long after, 420 million years ago, the first jawed fish appeared. The jawed fish proved to be very successful and the jawless fish declined, mostly going extinct at the end of the Devonian, 358 million years ago. The first jawed fish to appear, the Placoderms, were heavily armoured. They also went extinct at the end of the Devonian. Another early group were the Acanthodians or "spiny sharks" (they weren't sharks). The Acanthodians went extinct at the end of the Permian, 250 million years ago. The cartilaginous fish first appeared in the Middle Devonian, 395 million years ago. Today, three groups still exist: the chimaerae (also called elephantfish, ghostfish and rabbitfish), the sharks and the rays. The next major group of fish to appear, the bony fish or Osteichthyes appeared about 416 million years ago. They are made up of two groups: the Actinopterygii (the ray-finned fish) and the Sarcopterygii (the fleshy-finned fish). The former contains the vast majority of living fish. The latter includes the coelacanths, lungfish and the ancestors of the Tetrapods (amphibians, reptiles, birds and mammals).

(Acanthostega (Jarvik, 1952), an early tetrapodomorph)

The tetrapods first appeared about 395 million years ago, evolving from the sarcopterygian fish (although precisely which group is unclear at this time). Many tetrapods have been discovered, some resembling fish, some resembling amphibians and reptiles and others somewhere in between (dubbed "fishapods" by some). The exact placement of many of these taxa is unknown. But they are important because they were the forerunners of all amphibians, reptiles, birds and mammals that have ever existed.

(Euparkeria (Broom, 1913), an archosaur)

From those early tetrapodomorphs emerged all the amphibians, reptiles, birds and mammals. Other than when they first appeared, the amphibians have never really been the dominant animals on land. One of these early amphibian groups (and it's not clear which) gave rise to the amniotes. The amniotes are the reptiles, birds and mammals. They have been more successful than amphibians because they can lay their eggs in dry environments. Reptiles first appeared around 313 million years ago (Benton and Donoghue, 2007). Initially, it was the reptiles that gave rise to the mammals, the Synapsids, that ruled. This lasted until the Permian mass extinction, the largest mass extinction ever, wiped out nearly 90% of all life on Earth (Benton, 2005). After this extinction, the Diapsid reptiles (lizards, snakes, dinosaurs, crocodiles, pterosaurs, marine reptiles and possible tortoises) became more abundant. One of these groups, the Archosaurs, became the dominant terrestrial life forms from the Mid Triassic (Benton, 1983). From this group emerged the crocodiles, pterosaurs (maybe), birds and the dinosaurs.

And that brings us up to speed. As you can see, a lot happened before the Dinosaurs appeared. The next time-based post will be about the Mesozoic, the era in which the dinosaurs lived. However, the next post will be the second part of the Jurassic Park series, examining the issues surrounding the raptors.

See also:
More dinosaurs
Geochronology
Age of the Dinosaurs

References
Benton, M. (1983) 'Dinosaur Success in the Triassic: a Noncompetitive Ecological Model', Quarterly Review of Biology, 58 (1), pp. 29-55

Benton, M. (2005) When Life Nearly Died: The Greatest Mass Extinction of All Time, London: Thames & Hudson

Benton, M. and Donoghue, P. (2007) 'Paleontological Evidence to Date the Tree of Life', Molecular Biology and Evolution, 24 (1), pp. 26-53

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Broom, R. (1913) 'Note on Mesosuchus browni, Watson and on a new South African Triassic pseudosuchian (Euparkeria capensis)', Records of the Albany Museum, 2, pp. 394-396

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