Dino ‘puberty blues’ for paleontologists
Dinosaur juveniles and adults wrongly labelled as separate species
by David Catchpoole
Published: 15 June 2010(GMT+10)
Depictions of the animals boarding Noah’s Ark should take account of the way
that juvenile dinosaurs would have looked. So what did a young T. rex
look like? Something that paleontologists had given a different species name altogether!
Nanotyrannus was a bit like a Tyrannosaurus rex, except it had
17 teeth in its lower jaw, while a T. rex had 12 lower jaw teeth and a
less elongated skull.
However, now it seems that Nanotyrannus should never have been identified
as a separate species at all. Leading dinosaur paleontologist Dr Jack Horner of
Montana State University says that Nanotyrannus was in fact a juvenile
T. rex, whose skull changed dramatically as it matured. The transition
to adulthood also saw it trade its small, blade-like teeth to make room for a larger
set of adult teeth.
The Nanotyrannus mix-up came to light after a dinosaur mid-way between
a ‘Nanotyrannus’ and T. rex was discovered, which
had 14 lower jaw teeth.
Horner, with his paleontologist colleague Dr Mark Goodwin of the University of California,
cited this as just one of many examples of juvenile and adult dinosaurs having been
wrongly labelled as separate species. They suggest that as many as a third of all
known dinosaur species will need to be reclassified.1,2
Some paleontologists, e.g. Dr Hans-Dieter Sues of the National Museum of Natural
History in Washington, D.C., think that the estimate of one-third of dinos needing
reclassification might be an exaggeration. However, he does acknowledge that there
are indeed well-known instances of different species names being given to dinosaurs
that were in fact juveniles and adults of the same species. He explained that in
the 1970s paleontologists discovered that some duck-billed dinosaur species were
in fact merely at different stages of maturity—representing a smaller number
of species. “Many dinosaurs—just like many present-day vertebrates—changed
a lot in their appearance as they grew up,” he said.1
This announcement that one-third of dinosaur species ‘never existed’
follows an earlier analysis of the 1,401 scientific names given to dinosaurs from
1824 to 2004 which showed that about 16% of names were duplicates, and 32% embodied
other sorts of errors.
Of course, we can observe dramatic juvenile-to-adult transitions occurring today
in many land animals, e.g. those which have antlers and horns as adults, but not
as juveniles. And the physical changes are even more dramatic in amphibious vertebrates,
e.g. frogs, as they make the transition from tadpoles to adults. The tadpoles and
adult frogs are, of course, the same species. In birds, too, the physical
changes associated with the juvenile-to-adult transition can be dramatic. Hornbills,
for example, grow a distinctive helmet-like head casque. (Perhaps the head crests
served a similar function in the crested theropod dinosaurs?)
Horner and Goodwin noted very marked changes in the form of Triceratops
fossils that had died at various stages of life. They found that the youngest animals’
tiny straight horns changed as they got older—juvenile horns curving backward,
adult horns pointing forward. Also, the juveniles’ triangular spiked bones
surrounding the frill became flattened as the animal matured, lengthening into a
bony fan-like shield. Thus, despite the radically different appearance of juveniles
and adults, they are the same species.
The list goes on. E.g., we have featured Dracorex hogwartsia, ‘the
dinosaur that looks like a dragon’,3
pointing out that some paleontologists have suggested that it and Stygimoloch spinifer
are actually immature forms of Pachycephalosaurus wyomingensis.4 In other words, different names were unwittingly
given to juveniles and adults of the same creature.
This announcement that one-third of dinosaur species ‘never existed’
follows an earlier analysis of the 1,401 scientific names given to dinosaurs from
1824 to 2004 which showed that about 16% of names were duplicates, and 32% embodied
other errors.4–8 “It’s
a bit scary”, University of Bristol (UK) paleontologist Michael Benton said
at that time. He explained that paleontologists “were keen to name new species”
and would often “rush into print with new names for every odd leg bone, tooth,
or skull cap” they happened to find. “Later work, on more complete specimens,
reduced more than 1,000 named dinosaurs to 500 or so,” he said.9
And now the dinosaur ‘puberty blues’ have further forced paleontologists
to rethink dinosaur species classification—there have been way too
many dinosaur names. And even if the remaining acceptable dinosaur names still number
in the hundreds, Noah didn’t need to take those hundreds of named dinosaur
species aboard the Ark; just the representative kinds, as we shall
now explain further.
Dinosaurs on the Ark—‘species’ vs ‘kinds’; adults
vs juveniles
Photos by Don Batten
Skulls given different genus names Apatosaurus (top) and Diplodocus
(bottom) which are clearly the same biblical kind.
Now it is known that skulls which are less similar to each other (than are the above
two) are actually adult and juvenile forms of the same species.
The dramatic culling of dinosaur species names by paleontologists is right in line
with an important principle we set out in our past articles and other publications,
e.g. in chapters 13 and 19 of The Creation
Answers Book. We presented the skulls of Apatosaurus and Diplodocus
as an example of dinosaurs given different species names (not just species, in fact,
but different genus names) which are clearly the same biblical ‘kind’
(Genesis 1:24–25). We explained that the various kinds
of animals created by God would today mostly be represented by a larger grouping
than what is called a species. One common definition of a species is a group of
organisms that can interbreed, producing fertile offspring, and which does not mate
with other species. However, most of the so-called species within a particular genus
or family have not been tested to see what they can or cannot mate with—and
the dinosaurs, being presumed extinct, cannot be tested. But on the basis
of the striking similarities between Apatosaurus and Diplodocus
fossils, they were very clearly of the same biblical kind.
Creationist artist depictions of Noah watching his dinosaur passengers boarding
the Ark should no longer be drawn to show T. rex, but something more like
its juvenile form, Nanotyrannus
So Noah didn’t need to take an Apatosaurus pair and a Diplodocus
pair on board the Ark; rather, just two representatives of their one kind along
with all the other dinosaur kinds (Genesis 6:20)—of which it has been estimated previously
there were only 55 kinds.10
The announcement about the juvenile/adult transition of dinosaurs is useful to consider
not only in relation to the numbers of dinosaurs aboard the Ark, but also what the
Ark’s dinosaurian cargo looked like. For example, Noah didn’t need to
take a Dracorex pair and a Pachycephalosaurus pair onto the Ark,
but rather just the two Dracorex. That’s because, as we’ve
earlier pointed out, it makes much more sense that God brought juvenile dinosaurs
to Noah, rather than ‘grandma and grandpa’ dinos, given their purpose
was to repopulate the earth post-Flood.11
And similarly, creationist artist depictions of Noah watching his dinosaur passengers
boarding the Ark should no longer be drawn to show T. rex, but something
more like its juvenile form, Nanotyrannus.
Update, 4 August 2010: Triceratops on trial?
The famous dino Triceratops and the less well known Torosaurus
share the three horns, but the latter’s skull is much bigger—one of
the biggest of all land animals—and has two large holes, hence the name, meaning
‘perforated lizard’ (Greek τορέω toreō, to pierce or perforate
(not ‘bull lizard’, which would be Taurosaurus, from
Greek ταῦρος tauros). (Triceratops means ‘three-horned face’,
is derived from the Greek tri/tρι– three, keras/κέρας horn,
and –ōps/ωψ face.) Not surprisingly, their discoverer, Othniel
Marsh (1831–1899), classified them as different genera. But now, John Scannella
and Jack Horner at the Museum of the Rockies in Bozeman, Montana, argue that they
were the same species: Torosaurus was just a mature form of Triceratops.12
They noted that the skulls comprised metaplastic bone, a spongy blood-rich
bone that changes length over time. By counting growth rings, an age indicator somewhat
like tree rings (but see Tree ring dating
(dendrochronology)), they found that Triceratops specimens were
younger animals, while Torosaurus was much rarer and only adult speciments
were known. Also, the older Triceratops specimens had thinned regions of
the frill corresponding to the Torosaurus holes, suggesting that they were
transforming.
This also means that the frills would not have been very good shields—the
bone was too thin, and would bleed profusely.
This means that Torosaurus must be abolished as a separate taxon, since
by the naming rules, the first published name stands. Furthermore, the researchers
argue that previous classifications presumed that juvenile dinosaurs were just miniature
adults, but now we know that shape can change radically. So there are likely many
more dinosaur ‘genera’ that were really juveniles of other named genera.
So the Ark cargo was even lighter than previously thought.
A reader’s comment
Chavoux L., South Africa, 19 August 2010
Something else that I have thought about is the possibility of sexual dimorphism between males and females of the same species. I don’t really know how common it is in modern reptiles, but I think the possibility of it occurring in Dinosaurs has probably not been adequately researched.
Response by CMI’s Don Batten:
You have a good point. In reptiles living today, iguanas, for example, the males are significantly larger than the females, whereas with blind snakes the females are typically larger than the males. Male brown anole lizards are typically 2-3 times the weight of the females.
Creatures representing many diverse phyla show sexual dimorphism. Some of the extremes are the deep-sea angler fish, where the male is tiny and some spiders such as the black widow / redback, where the male is also tiny. This contrasts with sea lions, where the males are much larger than the females. Birds of course show some extremes of sexual dimorphism (the peacock/peahen, for example). With birds, sometimes it is the female that is showy and large, not the male. These inconsistencies make evolutionary story-telling to ‘explain’ sexual dimorphism rather difficult and self-contradictory.
One problem with dinosaurs is that no one really knows how to tell a female skeleton from a male one. Because T. rex eggs were relatively big, the hips of females might have been wider than males to allow for the passage of the eggs, but this is not certain. So there is disagreement about sexual dimorphism in dinosaurs. But it could certainly be a neglected factor that has contributed to the multiplication of species names. |
Related articles
References
- Handwerk, B., A third of dinosaur species never existed?,
National Geographic News,
http://news.nationalgeographic.com/news/2009/10/091009-dinosaur-species-never-existed.html,
9 October 2009. Return to text.
- Edwards, L., Researchers claim a third of dinosaurs might
never have existed,
http://www.physorg.com/news174634964.html, 13 October 2009. Return
to text.
- Fangrad, R.,
Dracorex—the dinosaur that looks like a dragon, 12 January 2007.
Return to text.
- Williamson, T. and 3 others, Early ontogeny of pachycephalosaurine
squamosals as revealed by juvenile specimens from the Hell Creek Formation, eastern
Montana, Journal of Vertebrate Paleontology 29(1):291–294,
2009. Return to text.
- Dalton, R., In search of Thingummyjigosaurus—There are
errors in almost half the names given to dinosaurs, <www.nature.com/news/2008/080917/full/news.2008.1111.html>,
17 September 2008. Return to text.
- Benton, M., Fossil quality and naming dinosaurs, Biology
Letters 4(6):729–732, 23 December 2008.
Return to text.
- Benton, M., How to find a dinosaur, and the role of synonymy
in biodiversity studies, Paleobiology 34(4):516–533,
December 2008. Return to text.
- Catchpoole, D., Too many
dinosaur names, 15 January 2009. Return to text.
- Amos, J., Will the real dinosaurs stand up? BBC News,
<news.bbc.co.uk/2/hi/science/nature/7620621.stm>, 17 September 2008.
Return to text.
- For more on this, see Sarfati, J., 2004,
Refuting compromise, chapters 7–8. Return to
text.
- Skeptics who claim Noah couldn’t have fitted all the
dinosaurs on board the Ark are wrong, as the Ark was easily big enough (Genesis 6:14–16) to accommodate 55 kinds of dinos
(along with all the other kinds of created animal and birds). Noah didn’t
need to take full-grown dinosaurs, but juveniles. Juveniles of even the largest
dinosaurs were less than 1 metre tall (about 3 ft)—see chapter 19 of
The Creation Answers Book; also see
Dr Jonathan Sarfati’s article about dinosaur growth rates.
Return to text.
- Scannella, J. and Horner, J.R.,
Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae:
Chasmosaurinae): synonymy through ontogeny, Journal of Vertebrate Paleontology
30(4):1157–1168, 2010 P-I-P-E doi:10.1080/02724634.2010.483632;
Lawton, G.,
Morph-osaurs: How shape-shifting dinosaurs deceived us, New Scientist
2771, 28 July 2010. Return to text.
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