When evolution just gives up, part 5
August 24, 2023
Why do you have to be this way, Camptosaurus?
August 19, 2023
Most dinosaurs are elegant animals. Tyrannosaurs are elegant biting machines. Chasmosaurs are elegent. Brachiosaurs are hella elegant. Even ankylosaurs have their own robust elegance.
And then there’s Camptosaurus.
Why do you have to be so lumpen? What’s your head doing down there? What the heck are your ilia doing up there? What are they even supposed to be, TV aerials?
Just look how impressed Matt is by this hunk of No Thanks:
Maybe Camptosaurus looks better from above?
Nope. Look how short its stupid neck is.
Ugh.
And if anything, the life reconstruction on the signage is even worse:
Just no, Camptosaurus. Just no.
How many animals have bifurcated cervical ribs?
August 13, 2023
BYU 14063, a left cervical rib of the turiasaur Moabosaurus in medial view.
A few sauropods have bifurcated cervical ribs. The most dramatic example that I know of is the turiasaur Moabosaurus (Britt et al. 2017). Mike and I got to see that material on the Sauropocalypse back in 2016, which is how we got the photo above. Royo-Torres et al. (2006) had previously described and figured bifurcated cervical ribs in Turiasaurus, but they seem to be absent in Mierasaurus (Royo-Torres et al. 2017), which is the sister taxon to Moabosaurus.
Cervical ribs of Dicraeosaurus from Janensch (1929). Note the dorsally-projecting bump on the shaft of the rib at the top.
Tschopp et al. (2015: character 217, p. 99–100, fig. 49) recognized a “posteriorly projecting spur on dorsolateral edge of [the] posterior shaft” of the cervical rib in Dicraeosaurus and some apatosaurines. That’s not a complete bifurcation, but it’s not a million miles out — at least, it’s implying that a second muscle was pulling on the cervical rib from a different direction as the first.
Sereno et al. (1999) reported that cervical ribs 3-6 of Jobaria have an “accessory anterior process”. This might mean that some of the anterior processes of the cervical ribs are bifurcated in Jobaria, but the character state is not illustrated and we have not been able to observe the relevant fossils firsthand.
Cervical ribs of Zhuchengceratops from Xu et al. (2010: fig. 7). Fifth cervical rib in lateral (I) and medial (J) views; sixth cervical rib in medial (K) and lateral (L) views.
Xu et al. (2010) described bifurcated cervical ribs in the leptoceratopsid ceratopsian Zhuchengceratops, including in their diagnosis “middle cervical ribs bifurcated due to presence of prominent accessory dorsal process (condition poorly known in other ceratopsians)”. The cervical ribs of Zhuchengceratops show a whole morphological spectrum, from an accessory dorsal process present as a tiny bump, as in Dicraeosaurus, all the way to full bifurcation. Xu et al. (2010) implied that this feature is also present in other ceratopsians including Triceratops.
So…who else? Any non-avian theropods? Weird Triassic hellasaurs? Attention-seeking salamanders? Cervical-rib-obsessed minds want to know.
References
- Britt, Brooks B., Rodney D. Scheetz, Michael F. Whiting and D. Ray Wilhite. 2017. Moabosaurus utahensis, n. gen., n. sp., a new sauropod from the Early Cretaceous (Aptian) of North America. Contributions from the Museum of Paleontology, University of Michigan 32(11):189–243.
- Janensch, Werner. 1929. Die Wirbelsäule der Gattung Dicraeosaurus. Palaeontographica, Supplement 7, 2:39–133 and plates I–VII.
- Royo-Torres, Rafael, Alberto Cobos and Luis Alcalá. 2006. A giant European dinosaur and a new sauropod clade. Science 314:1925–1927.
- Royo-Torres, Rafael, Paul Upchurch, James I. Kirkland, Donald D. DeBlieux, John R. Foster, Alberto Cobos and Luis Alcalá. 2017. Descendants of the Jurassic turiasaurs from Iberia found refuge in the Early Cretaceous of western USA. Scientific Reports 7:14311. doi:10.1038/s41598-017-14677-2
- Sereno, Paul C., Allison L. Beck, Didier. B. Dutheil, Hans C. E. Larsson, Gabrielle. H. Lyon, Bourahima Moussa, Rudyard W. Sadleir, Christian A. Sidor, David J. Varricchio, Gregory P. Wilson and Jeffrey A. Wilson. 1999. Cretaceous sauropods from the Sahara and the uneven rate of skeletal evolution among dinosaurs. Science 282:1342–1347.
- Xu X, Wang K, Zhao X, Sullivan C, Chen S. 2010. A new leptoceratopsid (Ornithischia: Ceratopsia) from the Upper Cretaceous of Shandong, China and its implications for neoceratopsian evolution. PLoS ONE 5(11): e13835. https://doi.org/10.1371/journal.pone.0013835
On the excellent and convivial social network Mastodon, someone going by the handle “gay ornithopod” asked what turned out to be a fascinating question:
What are your thoughts on how the coloration of sauropods would change as they matured? What would you expect to see for example on this guy in comparison with an adult?
My first response was that we can only say it’s not unusual for extant animals to change colour through ontogeny, so the null hypothesis would have to be that at least some sauropods (and other dinosaurs) did the same. But I don’t think we have any information on the specific coloration.
At this point Adam Yates chipped in to observe that:
While we can’t know (as already discussed), it is my experience that the overwhelming pattern is for colours to become duller and patterns more muted as animals age.
That was surprising to me. I found myself thinking about all the birds that hatch out an undistinguished brown color, and develop spectacular colours as they age. Adam pointed out:
Yes there are those, but for everyone of those I’ll show you a lizard, snake or crocodylian with wonderful, vivid colours and patterns when young that fades with age (classic example is the Komodo Dragon).
I hadn’t know that Komodo Dragons hatch as colourful little critters, before later adopting their classic muted grey-green colour, but check out the photos and videos at ZooBorns:
Beautiful.
So this is interesting: it seems birds do one thing (become more colourful through ontogeny) while crocs and other reptiles do the opposite.
So the phylogenetic bracket is of little use to us here. Somewhere along the line from the most recent common ancestor of birds and crocs to modern birds, the ontogenetic trajectory flipped … but where along that line? With what implications for other dinosaur groups?
It’s a decent bet that primitive dinosaurs such as Saturnalia retained the ancestral condition, and became progressively less flamboyant through ontogeny, whereas bird-like raptors such as our old buddy Velociraptor assumed their most colourful plumage later in life. But what about sauropods? I’m not sure there’s any way to tell.
In classic palaeoart, sauropods were always a uniform greenish grey or brownish grey, or just plain grey. In more modern palaeoart we are seeing far more interesting colours and patterns: for example, the vivid black/white contrasts in John Conway’s Dreadnoughtus:
But if such patterning did occur, was it in juveniles or adults? (Or both, of course.)
I would like to understand why crocs and lizards have the trajectory they do. It’s easy to understand that juvenile birds are nondescript to avoid predation, but adults become more visible to attract mates. But how does the opposite trend make any sense? How is it of use to baby lizards to be highly visible?
Thoughts?
Brian Curtice, a long-time sauropod jockey who now runs Fossil Crates, was briefly in Price, Utah, last Friday to drop off an Eilenodon skull at the Prehistoric Museum. While he was there he snapped some photos of a new “Dippy” exhibition — reproduced here with permission.
The entrance to the exhibition. Unfortunately the sign obscures much of what’s beyond (and what is it with this ridiculous nickname “Dippy”? Come on! Give this animal some dignity.) But it does show that there are a lot of elements on display, including the dorsal sequence (to the left), the proximal tail (to the right) and a hindfoot (bottom right, partly obscured by the pillar).
All these elements are of course the concrete casts made in 1957 by the Untermanns and their colleagues at the Utah Field House of Natural History in Vernal. They have been really nicely restored, as other photos show.
A complete set of right-sided dorsal ribs:
A probably proximal humerus and coalesced tradius/ulna pair:
I won’t labour the point, but there’s also a full hindlimb — femur, tib/fib, astragalus, pes — whiplash tail (last 30 or so caudals) and quite possibly more than Brian didn’t get photos of.
Of course, the museum is keen to find a way to mount these concrete bones, but the irony is that right now, having all those cast elements on display in a well-lit hall makes this possibly the world’s most informative exhibit of sauropod osteology. If you want to see how morphology changes along the first ten caudals, for example, this is going to be so much easier to access than the original Carnegie Museum material, up way above head-height in its mount.
Anyway: the other great thing about this exhibit is the signage. There is a lot of it — Brian sent photos of 40 or so panels, with accessible but informative text and plenty of historic photos.
But the most gratifying thing for me about the signage is that evidently a lot of it was drawn from material in our paper The Concrete Diplodocus of Vernal (Taylor et al. 2023), including for example this section on what happened to the original molds:
I love the idea that our paper is now out there reaching regular people and helping to tell the fascinating story of that concrete dinosaur.
I’d love to visit it myself, if it’s there long enough.
References
Sauropod Vertebra Picture of the Week 