SVP 2025 abstracts of interest 8

It’s SVP abstracts season!!!
Here is part 8 of 10, oddly the second half of the alphabet for lead authors.

Developmental mechanisms of axial evolution in stem and crown cetaceans (Mammalia, Artiodactyla)

Martin-Serra et al (p410)
“The land-to-sea transition of cetaceans is one of the major events in the evolution of mammals, as it conveyed profound changes in the mammalian body plan.”

Make that >twoOdontocetes are not related to mysticetes. If they are still teaching university students that mysticetes were related to odontocetes save your tuition money.

“As a consequence, the backbone can change in different ways, such as varying the number of vertebrae (somitogenesis), their identity (thoracic, lumbar, etc. related to homeotic changes) and their length (somatic growth). In this study, we have quantified these three developmental mechanisms in a phylogenetic context of stem and crown cetaceans.”

This study is hobbled by following and promoting the myth of cetacean monophyly.

“Our results indicate that the main mechanism involved in the evolution of the thoracic length relative to lumbar length is the somitogenesis (changes of the number of vertebrae), more specifically the increase of the number of lumbar vertebrae.”

Be specific. Caperea (Fig 1) has 0 lumbars. Eschrichtius has 9 among mysticetes. Tenrecs have 6 lumbars. So does Maiacetus. Physeter has 7. Oricinus has 10, Tursiops has 13. Basilosaurus has 21 elongate lumbars.

“the caudal region, the changes in the relative length is caused by a combination of somitogenesis and somatic growth (caudal vertebrae change in length and number).”

Among odontocetes I don’t see a trend to more caudals than Pakicetus has, but the caudals are taller. Basilosaurus is the exception with 26 caudals. Among mysticetes and their ancestors, desmostylians have vestigial tails. Caperea (Fig 1) has 12 caudals that diminish in size caudally. Eschrictius has 28 raller caudals with deeper chevrons. Eubalaena has 16 with taller neural spines and tiny chevrons.

“they possess a fused sacral region.”

In both odontocetes and mysticetes (Fig 1) the sacral ‘region’ is comprised of only one vertebra – not fused, and not attached to the pelvis.

The anatomy of the carpus and tarsus of squamates provides novel morphologic
support for key molecular clades

Meyer (p429)

“Squamate origin and early evolution remains obscured by persistent conflict in phylogenies generated by morphologic and molecular data.”

Glad to see someone else also recognizes the conflict. Now what will they do about it?

“I used 3D μCT imagery of modern lizards from every limbed-family (n = 84) to generate comparative images (>10,000) of the individual carpal and tarsal elements across Squamata, creating the first 3D atlas of their anatomy.”

A big database is essential. A tip of the hat to the only person on the planet who generated 10,000 images of carpal and tarsal elements across Squamata. However, I would consider this not that useful. Use all the traits from nose to tail tip to establish hypothetical interrelationships. Don’t focus on carpals and tarsals.

Detailed anatomy of the neotype of Amphibamus grandiceps (YPM 794) revealed by high contrast micro-CT analysis

Montgomery et al (p439)
“Amphibamus is a historically important species for establishing the relationship between Paleozoic temnospondyls and modern lissamphibians,”

In the large reptile tree (LRT, 2440 taxa) late Carboniferous Amphibamus is a basal reptilomorph nesting between microsaurs and other reptilomorphs including Late Devonian Tulerpeton. Despit this, note the lack of ossification in the carpals and tarsals along with the other limb joints. This appears to be a juvenile, still growing and ossifying.

“The results of our CT analysis reveal and clarify several anatomical features in YPM 794, including the incomplete distal ossification of the caudal vertebrae, a presacral count of 18 vertebrae, lack of an interclavicle, and presence of a short and rounded snout. This last feature appears to differ from several other specimens referred to as Amphibamus, including FMNH UC 2000, which has a narrow and blunt snout.”

No phylogenetic change was reported following the updates of their µCT scans.

Convergent evolution in endocranial morphology of pterosaurs and birds: how the brain shapes locomotory behaviors in archosaurs

Morgan et al (p443)
“until now no one has brought together a large comparative dataset to understand how their neuroanatomy compares to that of other archosaurs, including crown-group birds.”

That’s good. I like workers who put together large datasets for the purpose of comparative anatomy. However, since Peters 2000 pterosaurs have not been archosaurs (= crocs + dinos only) and since Peters 2007 pterosaurs have been lepidosaurs.

“although the avian and pterosaur lineages evolved powered flight independently and using drastically divergent wing morphologies, their neuroanatomy converged extensively.”

That makes sense. Odontocetes and mysticetes also converged extensively.

Evaluating the contributions of phylogeny and substrate preference on intracranial morphology in extant and extinct Xenarthra

Narducci (p453)
“Xenarthrans (anteaters, armadillos, and sloths) are a New World radiation that are today
represented by 31 species.”

That’s what oudated texbooks report. In the LRT anteaters and armadillos are closer to insectivorous sengis sharing a tube-like snout and other traits, while unrelated herbvorous sloths are closer to bulky Barylambda (Fig 4), sharing a box-like snout and other traits. Similarities are thus the result of convergence.

“The 1st PC (= princiipal component) axis demonstrated clear separation in endocranial shape between cingulates (armadillos) and the two groups of pilosans (anteaters and sloths).”

Better to use good old phylogenetic analysis over a wider than you think you need list of pertinent taxa. Look at competing hypotheses of interrelationships.

CT-derived morphological data reveals early musculoskeletal adaptations in Archaeopteryx

O’Connor et al (p465)
“Here we present new morphological data from the first scan of the nearly complete, exceptionally well-preserved Chicago specimen of Archaeopteryx.”

The authors don’t realize (or choose not to realize) the phylogenetic variety in Solnhofen birds, so these lumpers naively call ALL OF THEM Archaeopteryx. The LRT lumps and splits the more complete specimens and the Chicago specimen does not nest with the holotype skeleton.

“Our reconstruction reveals the skull is proportionately longer than previously recognized.”

That’s because it is a different genus.

“Furcular morphology supports a close relationship with Anchiornis and suggests a cartilaginous sternum was present.”

The LRT nests the Chicago specimen at the base of the Scansoriopteryx clade.

Source: https://pterosaurheresies.wordpress.com/2025/11/19/svp-2025-abstracts-of-interest-8/