Giant Mesozoic flat heads: Siderops and Koolasuchus

Little Gerrothorax has a new giant sister, Siderops,
(Fig. 1) in the large reptile tree (LRT, 1440 taxa). This is a traditional nesting recovered by prior workers.

We’re still missing those poorly ossified fingers and toes.
Or did this clade have lobefins (Fig. 2)? Nothing past the wrist is known for any clade members (that I’ve seen). Could go either way with available data… so, don’t assume fingers and toes.

Figure 1. Siderops in several views from Warren and Hutchinson 1983, colors added. The related giant Koolasuchus and small Gerrothorax are added for scale.

Figure 1. Siderops in several views from Warren and Hutchinson 1983, colors added. The related giant Koolasuchus and small Gerrothorax are added for scale. Are these lobefins or did they have feet? And look at the size of those palatal fangs!

Speaking of clades,
both Siderops and Gerrothorax are traditionally considered temnospondyls, which all have fingers and toes. Here they nest prior to traditional temnospondyls, closer to flathead lobefin tetrapods, like Tiktaalik, in the LRT (subset Fig. 2).

Figure 1. Subset of the LRT focusing on basal tetrapods and showing those taxa with lobefins (fins) and those with fingers and toes (feet). Inbetween we have no data.

Figure 2. Subset of the LRT focusing on basal tetrapods and showing those taxa with lobefins (fins) and those with fingers and toes (feet). Inbetween we have no data.

Siderops kehli (Warren and Hutchinson 1983; Early Jurassic, 180mya; skull 50cm long, overall 2.5m long) was traditionally considered a chigutisaurid temnospondyl or a brachyopoid. Here Siderops nests with the much smalller Gerrothorax. No branchials and scales were reported. The back of the skull and the extremities are unknown, so modifications were made to reflect that lack of data here.

Koolasuchus cleelandi was a late surviving Early Cretaceous giant from this clade, presently known from just a few bones, like the mandible (Fig. 2).

Tomorrow we’ll take a look
at several giant ‘amphibians’ (= anamniote tetrapods) all to scale.


References
Warren A and Hutchinson M 1983. The last labyrinthodont? A new brachyopoid (Amphibia, Temnospondyli) from the Early Jurassic Evergreen Formation of Queensland, Australia. Philosophical Transactions of The Royal Society B Biological SciencesB 303:1–62.

wiki/Gerrothorax
wiki/Siderops

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Why do human males develop facial hair?

Distinct from other apes,
human males develop facial hair at puberty that creates a beard and mustache. Then many men shave it off. If you’ve ever wanted to know why, here are some recent hypotheses.

According to the BBC online, “beards probably evolved at least partly to help men boost their standing among other men.” because women are not more interested in men with beards. “To reproduce, it’s often not enough to simply be attractive. You also have to compete with the same sex for mating opportunities.”

“A man’s ability to grow a fulsome beard isn’t actually neatly linkedto his testosterone levels. “

“Both men and women perceive men with beards as olderstronger and more aggressive than others. And dominant men can get more mating opportunities by intimidating rivals to stand aside.”

Figure 1. Percent of body hair on males worldwide appease here in darker tones. Both equatorial and polar humans have less hair. Mediterranean and Scandinavian men have more hair covering their bodies.

Figure 1. Percent of body hair on males worldwide appease here in darker tones. Both equatorial and extreme polar humans have less hair. Mediterranean and Scandinavian men have more hair.

“Men on average also think their body should be more muscular than women report that they want, while women on average believe they need to be thinner and wear more make-up than men report that they want.”

“Make-up use, average body composition, and even the very ability to grow facial hair all differ enormously across the world – meaning we could get different results elsewhere.”

This BBC article originally appeared on The Conversation (links below).


References
Dixson A DSc, Dixson B and Anderson M 2005. Sexual Selection and the Evolution of Visually Conspicuous Sexually Dimorphic Traits in Male Monkeys, Apes, and Human Beings, Annual Review of Sex Research, 16:1, 1-19, DOI: 10.1080/10532528.2005.10559826

http://www.bbc.com
https://theconversation.com

Cope’s Rule vs. Phylogenetic Miniaturization

Getting bigger
Wikipedia reports, Cope’s rule, named after American paleontologist Edward Drinker Cope, postulates that population lineages tend to increase in body size over evolutionary time. It was never actually stated by Cope, although he favoured the occurrence of linear evolutionary trends.”

Getting smaller
On the other hand, there is no Wikipedia category for Phylogenetic Miniaturization, which postulates that population lineages tend to decrease in body size over evolutionary time.

Both have their time and place.
For instance, if you take a look at the large reptile tree (LRT, 1026 taxa) in the mammal subset you’ll find the following taxon pairs representing Cope’s Rule:

  1. Toxodon is a giant Dromiciops
  2. Panthera (lion) is a giant Procyon (raccoon)
  3. Homo (human) is a giant Ptilocercus (tree shrew)
  4. Physeter (sperm whale) is a giant Tenrec (tenrec)
  5. Balaenoptera (blue whale) is a giant Ocepeia
  6. Giraffa (giraffe) is a giant Cainotherium
  7. Elephas (elephant) is a giant Procavia (hyrax)
  8. Ceratotherium (rhino) is a giant Hyracodon
  9. Paraceratherium is a giant Mesohippus.
  10. And in pterosaurs…Pteranodon is a giant Germanodactylus
  11. Quetzalcoatlus is a giant TM10341

Note:
these are general trends, not always direct lineages. We’ll never find the exact ancestors of living or fossil taxa, though we can get very close! Employed taxa represent evolutionary stages, sets of derived characters mixed with some small or large number of autapomorphic traits not shared by the unknown common ancestor of the small and large taxon pairs.

Likewise
you’ll also find in the LRT the following taxon pairs representing examples of phylogenetic miniaturization, some from the large pterosaur tree:

  1. Gephyrostegus is a tiny Proterogyrinus
  2. Terrapene (box turtle) is a tiny Elginia
  3. Cosesaurus is a tiny Macrocnemus
  4. Hypuronector is a tiny Jesairosaurus
  5. Bellubrunnus is a tiny Campylognathoides
  6. TM 13104 is a tiny Scaphognathus
  7. Tetrapodophis is a tiny Adriosaurus
  8. Hadrocodium is a tiny Haldanodon.
  9. Elaschistosuchus is a tiny Proterosuchus
  10. Gracilisuchus is a tiny Vjushkovia.
  11. Archaeopteryx is a tiny Sinornithoides.

What goes down (gets smaller), usually goes up (gets bigger)
And sometimes what gets bigger gets smaller. Case in point: the Pygmy or Channel Islands mammoth.

Anything can happen at any time in evolution
given enough time. As noted earlier, phylogenetic miniaturization was present at the origin of several major clades of tetrapods and in clades of pterosaurs in particular. And this appears to occur during times of survival stress for several reasons. On the other hand, apparently it takes an epoch filled with plenty of food and other resources to produce giant animals. As you know, various parts of the Earth have created stress and bounty throughout its long prehistory.

Sperm whales have faces, too!

Figure 1. This image comes from a news story on whale strandings and the contents of their stomachs. But I see two distinct faces here, like humans, chimps and other mammals with distinctive coloration patterns and variations on morphology.

Figure 1. This image comes from a news story on whale strandings and the contents of their stomachs. But I see two distinct faces here, like humans, chimps and other mammals with distinctive coloration patterns and variations on morphology.

Humans have distinct faces.
So do chimps, dogs, cows, other mammals and animals in general. We just have to see two in close proximity (as in Fig. 1) to notice the slight variation that Nature puts on pod mates and/or family members. This minor variation, of course, is the engine by which large variation can add up in isolation to produce new species, whether larger or smaller, more robust or more gracile, shorter, longer, with longer or shorter limbs, longer or shorter faces. The variations are endless, but patterns can be gleaned in phylogenetic analysis.

Look closely
and you’ll see the profile of these two beached whales are slightly different, the flippers are slightly different, to say nothing of the variations on the white patches and scars that they are partly born with and then develop during their lifespan as white scars.

Just think,
this odontocete is derived from swimming tenrecs, derived from basal placentals, derived cynondonts, etc. etc. all due to subtle variations in family members like you see here, over vast stretches of time and millions of generations.

Trimerorhachis and kin to scale

Updated April 23 with a revision to the tabulars of Panderichthys. Thanks DM! My bad. 

Yesterday we took a revisionary look at Trimerorhachis insignis (Cope 1878, Case 1935, Schoch 2013; Early Permian; 1m in length; Fig. 1). Today we take a quick peek at the taxa that surround it in the large reptile tree (LRT, 980 taxa, Fig. 1) all presented to scale. Several of these interrelationships have gone previously unrecognized. Hopefully seeing related taxa together will help one focus on their similarities and differences.

Figure 1. Trimerorhachis and kin to scale. Here are Panderichthys, Tiktaalik, Ossinodus, Dvinosaurus, Acanthostega, Batrachosuchus and Gerrothorax. Maybe those tabular horns on Acanthostega are really supratemporal horns, based on comparisons to related taxa.

Figure 1. Trimerorhachis and kin to scale. Here are Panderichthys, Tiktaalik, Ossinodus, Dvinosaurus, Acanthostega, Batrachosuchus and Gerrothorax. Maybe those tabular horns on Acanthostega are really supratemporal horns, based on comparisons to related taxa.

And once again
phylogenetic miniaturization appears at the base of a tetrapod clade. Note: the small size of Trimerorhachis (Fig. 1) may be due to the tens of millions of years that separate it in the Early Permian from its initial radiation in the Late Devonian, at which time similar specimens might have been larger. Provisionallly, we have to go with available evidence.

We start with…

Panderichthys rhombolepis (Gross 1941; Frasnian, Late Devonian, 380 mya; 90-130cm long; Fig. 1). Distinct from basal taxa, like Osteolepis, Pandericthys had a wide low skull, a wide low torso, a short tail and five digits (or metacarpals). No interfrontal was present. The orbits were further back and higher on the skull. Dorsal ribs, a pelvis and large bones within the four limbs were present.

Tiktaalik roseae (Daeschler, Shubin and Jenkins 2006; Late Devonian, 375mya: Fig. 1) nests between Pandericthys and Trimerorhachis in the LRT. Distinct from Panderichthys the opercular bones were absent and the orbits were even further back on the skull.

Ossinodus pueri (Warren and Turner 2004; Viséan, Lower Carboniferous; Fig. 1) was orignally considered close to Whatcheeria. Here it nests between Trimerorhachis and Acanthostega. The presence of an intertemporal appears likely. Distinct from Acanthostega, the skull is flatter, the naris is larger. Distinct from sister taxa, the maxilla is deep and houses twin canine fangs. A third fang arises from the palatine.

Acanthostega gunnari (Jarvik 1952; Clack 2006; Famennian, Late Devonian, 365mya; 60cm in length; Fig. 1) was an early tetrapod documenting the transition from fins to fingers and toes. Based on its size and placement, the nearly circular bone surrounding the otic notch is here identified as a supratemporal, not a tabular, which appears to be lost or a vestige fused to the supratemporal. This taxon is derived from a sister to Ossinodus and appears to have been an evolutionary dead end.

Trimerorhachis insignis (Cope 1878, Case 1935, Schoch 2013; Early Permian; 1m in length; Fig. 1) was considered a temnospondyl close to Dvinosaurus, but here nests as a late surviving basal tetrapod from the Late Devonian fin to finger transition. It is close to Ossinodus and still basal to Dvinosaurus (Fig. 1) and the plagiosaurs. As a late survivor, Trimerorhachis evolved certain traits found in other more derived tetrapods by convergence, like a longer femur and open palate. The presence of a branchial apparatus indicates that Trimerorhachis had gills in life. Dorsally Trimerorhachis was covered with elongated scales, similar to fish scales.

Dvinosaurus primus (Amalitzky 1921; Late Permian; PIN2005/35; Fig. 1) Dvinosauria traditionally include Neldasaurus among tested taxa. Here Dvinosaurus nests basal to plagiosaurs like Batrachosuchus and Gerrothorax and was derived from a sister to Trimerorhachis.

Batrachosuchus browni (Broom 1903; Early Triassic, 250 mya; Fig. 1) nests with Gerrothorax, but does not have quite so wide a skull.

Gerrothorax pulcherrimus (Nilsson 1934, Jenkins et al. 2008; Late Triassic; Fig. 1) was originally considered a plagiosaurine temnospondyl. Here it nests with the Trimerorhachis clade some of which  share a lack of a supratemporal-tabular rim, straight lateral ribs and other traits.

This clade of flathead basal tetrapods
is convergent with the flat-headed Spathicephalus and Metoposaurus clades and several others.

References
Berman DS and Reisz RR 1980. A new species of Trimerorhachis (Amphibia, Temnospondyli) from the Lower Permian Abo Formation of New Mexico, with discussion of Permian faunal distributions in that state. Annals of the Carnegie Museum. 49: 455–485.
Broom R 1903. On a new Stegocephalian (Batrachosuchus browni) from the Karroo Beds of Aliwal North, South Africa. Geological Magazine, New Series, Decade IV 10(11):499-501
Case EC 1935. 
Description of a collection of associated skeletons of Trimerorhachis. University of Michigan Contributions from the Museum of Paleontology. 4 (13): 227–274.
Clack JA 2006. The emergence of early tetrapods. Palaeogeography Palaeoclimatology Palaeoecology. 232: 167–189.
Clack JA 2009. The fin to limb transition: new data, interpretations, and hypotheses from paleontology and developmental biology. Annual Review of Earth and Planetary Sciences. 37: 163–179.
Coates MI 2014. The Devonian tetrapod Acanthostega gunnari Jarvik: Postcranial anatomy, basal tetrapod interrelationships and patterns of skeletal evolution. Earth and Environmental Science Transactions of the Royal Society of Edinburgh.
Coates MI and Clack JA 1990. Polydactly in the earliest known tetrapod limbs. Nature 347: 66-69.
Colbert EH 1955. Scales in the Permian amphibian. American Museum Novitates. 1740: 1–17.
Daeschler EB, Shubin NH and Jenkins FA, Jr 2006. A Devonian tetrapod-like fish and the evolution of the tetrapod body plan. Nature. 440 (7085): 757–763.
Gross W 1941. Über den Unterkiefer einiger devonischer Crossopterygier (About the lower jaw of some Devonian crossopterygians), Abhandlungen der preußischen Akademie der Wissenschaften Jahrgang.
Jarvik E 1952. On the fish-like tail in the ichtyhyostegid stegocephalians. Meddelelser om Grønland 114: 1–90.
Jenkins FA Jr, Shubin NH, Gates SM and Warren A 2008. Gerrothorax pulcherrimus from the Upper Triassic Fleming Fjord Formation of East Greenland and a reassessment of head lifting in temnospondyl feeding. Journal of Vertebrate Paleontology. 28 (4): 935–950.
Nilsson T 1934. Vorläufige mitteilung über einen Stegocephalenfund aus dem Rhät Schonens. Geologiska Föreningens I Stockholm Förehandlingar 56:428-442.
Olson EC 1979. Aspects of the biology of Trimerorhachis (Amphibia: Temnospondyli). Journal of Paleontology. 53 (1): 1–17.
Pawley K 2007. The postcranial skeleton of Trimerorhachis insignis Cope, 1878 (Temnospondyli: Trimerorhachidae): a plesiomorphic temnospondyl from the Lower Permian of North America. Journal of Paleontology. 81 (5):
Warren A and Turner S 2004. The first stem tetrapod from the Lower Carboniferous of Gondwana. Palaeontology 47(1):151-184.
Williston SW 1915. 
Trimerorhachis, a Permian temnospondyl amphibian. The Journal of Geology. 23 (3): 246–255.
Williston SW 1916. The skeleton of Trimerorhachis. The Journal of Geology. 24 (3): 291–297.

 

wiki/Ossinodus
wiki/Acanthostega
wiki/Tiktaalik
wiki/Panderichthys
wiki/Trimerorhachis
wiki/Gerrothorax
wiki/Batrachosuchus

Carroll 1988

Figure 1. Vertebrate Paleontology by RL Carroll 1988.

Figure 1. Vertebrate Paleontology by RL Carroll 1988 is one of the starting points for this blog and ReptileEvolution.com

In 1988
Dr. Robert L. Carroll published a large work devoted to the study of fish and tetrapods: Vertebrate Paleontology and Evolution. Between its black covers and silver dust jacket there was – and is – an immense amount of data on just about every taxon known at the time… a time just before software driven phylogenetic analysis became de rigueur.

My copy
has been used so much it has a broken binder, which makes every section lighter, easier for scanning.

For its time, and for a few decades later
Vertebrate Paleontology and Evolution was the ‘go-to’ textbook for students and artists of this science. (See below).

A few quotes from the Amazon.com website:

  1. “This book was my textbook for Vertebrate Paleontology and Evolution at the University of Rochester back in 1992.”
  2. “the only easily available work that goes to any depth on this intensely interesting subject.”
  3. “The book is very daunting to look at if you just flip through it. However, it does a nice job of introducing concepts and terms to the reader. Its organization is straightforward, starting with the simplest vertebrates and eventually finishing with mammals.:
  4. “Just realize that some of the information may not reflect our current understanding since the book is over 10 years old and many new finds have come to light, new ideas have been introduced, and old ideas reexamined.”
  5. “It’s an essential for anyone building a library of paleo textbooks.”
  6. “I’m a working fossil preparator and this is the primary reference text used in paleontology labs at the American Museum of Natural History, Yale Peabody Museum and others I’m sure.”
  7. “I had Romer’s Vertebrate Paleontology, which is an excellent book, until a paleontologist friend directed me to Carroll’s book. He acknowledges Romer’s work in the field but this is an updated version (for the time of publication).”
  8. “If you want to chart the course of evolution up to the present – read this book!”

Carroll 1988 updated
Romer’s Vertebrate Paleontology  (1933, 1945, 1966) which was the ‘go-to’ textbook of its day.

ReptileEvolution.com
updates portions of Carroll 1988. Likewise and in due course, someone someday may want to update ReptileEvolution.com. I hope they do so.

Every so often
it’s good to give credit to one’s mentors and resources. Sometimes you learn by doing. Other times you learn by reading. I suppose everyone who writes such a large gamut book knows he/she is doing something to help future students and enthusiasts who they will never meet. I feel the same way, butI imagine both Carroll and Romer were additionally warmed by a healthy royalty check once or twice a year.

References
Carroll RL 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Co. New York.
Romer AS 1966. Vertebrate Paleontology. University of Chicago Press, Chicago; 3rd edition

wiki/Vertebrate_Paleontology_and_Evolution

Zhenyuanlong: Dromaeosaur? No. Tyrannosaur with wings? Yes.

Lü and Brusatte 2015
described a short-armed, winged Early Cretaceous Liaoning theropod, Zhenyuanlong suni (Fig. 1, JPM-0008 Jinzhou Paleontological Museum), as a dromaeosaur. Their published phylogenetic analysis included only dromaeosaurs but their text indicates a large inclusion set.

Figure 1. Zhenyuanlong in situ with colors applied to bones and feathers. These colors are transferred to create the reconstruction in figure 3.

Figure 1. Zhenyuanlong in situ with colors applied to bones and feathers. These colors are transferred to create the reconstruction in figure 3. The pelvic elements are reconstructed at right. The manus and pes are reconstructed at left.  Scale bars are 10cm.

From the Lü and Brusatte text
“We included Zhenyuanlong in the phylogenetic dataset of Han et al., based on the earlier analysis of Turner et al, which is one of the latest versions of the Theropod Working Group dataset. This analysis includes 116 taxa (two outgroups, 114 ingroup coelurosaurs) scored for 474 active phenotypic characters. Following Han et al., characters 6, 50, and 52 in the full dataset were excluded, 50 multistates were treated as ordered, and Unenlagia was included as a single genus-level OTU. The analysis was conducted in TNT v1.142 with Allosaurus as the outgroup.”

I reconstructed this theropod,
from published photographs (Figs. 1, 2) using (DGS digital graphic segregation), added it to the large reptile tree and found that it nested between tiny Compsognathus and gigantic Tyrannosaurus rex. Of course, Zhenyuanlong had the opportunity to nest with several dromaeosaurs, but it did not do so.

Figure 2. Skull of Zhenyuanlong in situ, as originally traced, colorized with skull, palate and mandible segregated.

Figure 2. Skull of Zhenyuanlong in situ, as originally traced, colorized with skull, palate and mandible segregated. Original quadrate may be a quadratojugal.

When you look at the reconstruction,
(Fig. 3) the similarity to T. rex becomes immediately apparent… except for those long feathered wings, of course.

I’ll run through several of the traits that link
Zhenyuanlong to Tyrannosaurus to the exclusion of dromaeosaurs here. It’s a pretty long list. Even so, if you see any traits that should not be listed, let me know and why.

  1. skull not < cervical series length
  2. skull not < half the presacral length
  3. premaxilla oriented up
  4. lacrimal not deeper than maxilla
  5. naris dorsolateral
  6. naris at snout tip, not displaced dorsally
  7. orbit length < postorbital skull
  8. orbit not > antorbital fenestra
  9. orbit no > lateral temporal fenestra
  10. orbit taller than wide
  11. frontal with posterior processes
  12. posterior parietal inverted ‘B’ shape
  13. jugal posterior process not < anterior
  14. parietal strongly constricted
  15. quadratojugal right angle
  16. majority of quadrate covered by qj and sq
  17. postorbital extends to minimum parietal rim
  18. maxillary teeth at least 2x longer than wide
  19. mandible tip rises
  20. angular not a third of mandible depth
  21. retroarticular process expands dorsally and ventrally
  22. cervicals taller than long
  23. cervicals decrease cranially
  24. mid cervical length < mid dorsal
  25. caudal transverse processes present beyond the 8th caudal
  26. humerus/femur ratio < 0.55
  27. metacarpals 2 & 3 do not align with manual one joints
  28. pubis angles ventrally – not posteriorly
  29. 4th trochanter of femur sharp
  30. metatarsals 2 & 3 align with p1.1
Figure 3. Zhenyuanlong reconstructed in lateral view. Something behind the pelvis could be the remains of an egg, but needs further study. Both sets of wing feathers are superimposed here. Click to enlarge.

Figure 3. Zhenyuanlong reconstructed in lateral view. Something behind the pelvis could be the remains of an egg, but needs further study. Both sets of wing feathers are superimposed here. Click to enlarge. Note the pubis is not oriented posteriorly. Note the longer legs of Zhenyuanlong compared to tested dromaeosaurs.

Shifting
Zhenyuanlong to the dromaeosaurs adds a minimum of 127 steps to the large reptile tree. There is one clade of theropods that nests between the current tyrannosaur and dromaeosaur clades.

Figure 3. Cladogram subset of the large reptile tree showing the strong nesting of Zhenyuanlong as the current sister to Tyrannosaurus. Obviously many more theropod taxa are missing here. They have not been tested yet.

Figure 4. Cladogram subset of the large reptile tree showing the strong nesting of Zhenyuanlong as the current sister to Tyrannosaurus. Obviously many more theropod taxa are missing here. They have not been tested yet.

Note
I have not tested as many theropods as there are in several theropod cladograms.

The possible faults with the Lü and Brusatte study were

  1. a lack of reconstructions to work with, rather than just a score sheet that others had created and they trusted. Reconstructions test identifications by making sure the puzzle pieces actually fit, both morphologically and cladisitically.
  2. I think they were fooled by the apparent posterior orientation of the pubis in situ when in vivo it was not oriented posteriorly
  3. I’m guessing that the traits they used could be used on in situ fossils without making reconstructions. The traits I use require reconstructions.
Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

Figure 0. Taxa ancestral to tyrannosaurs beginning with the CNJ7 specimen of Compsognathus.

With this nesting
the origin of long pennaceous wing feathers is evidently more primitive than earlier considered, developed twice. And perhaps this is why T. rex had such tiny arms. They were former wings, not grasping appendages.

References
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.