svp abstracts of interest or bombast 2024: O–Q

It is abstract season.
Here are selected sentences from selected abstracts from SVP 2024 – Minneapolis:

O’Connor J et al: Chicago Archaeopteryx reveals early transformations in the avian skull. (Examined earlier here out of alphabetical order).

Figure 1. Click to enlarge. Gephyrostegus moves to the base of the Archosauromorpha with its long-legged, hump-backed relatives. ” data-image-caption=”

Figure 1. Click to enlarge. Gephyrostegus moves to the base of the Archosauromorpha with its long-legged, hump-backed relatives.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/11/basal-amniotes-to-scale588-1.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/11/basal-amniotes-to-scale588-1.jpg?w=584″ class=”size-full wp-image-62509″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2021/11/basal-amniotes-to-scale588-1.jpg” alt=”Figure 1. Click to enlarge. Gephyrostegus moves to the base of the Archosauromorpha with its long-legged, hump-backed relatives.” width=”584″ height=”580″ />

Figure 1. Click to enlarge. Gephyrostegus moves to the base of the Archosauromorpha with its long-legged, hump-backed relatives.

Peecook BR et al: The amniote common ancestor was “synapsid”.
“Patterns of temporal fenestration have been central to taxonomies and evolutionary
scenarios for amniote evolution for most of the history of paleontology. Indeed the singleholed ‘synapsid’ condition of the mammal crown group and the doubly-holed ‘diapsid’ condition of the reptile crown group largely hold up (with notable modifications).”

The LRT refutes this hypothesis with dual convergent origins for diapsid and synapsid  morphologies (= 2 synapsids + 2 diapsids)

“The early evolution of reptiles has been particularly problematic with the positions of unfenestrated ‘anapsid’ protorothyridids, captorhinids, and ‘parareptiles’ implying multiple origins of temporal fenestration within Amniota.”

Run a wide gamut analysis of genera to confirm convergent diapsid and synapsid skull architectures..

“1) Protorothryrididae and Captorhinidae are stem-amniotes and their ‘anapsid’ skulls are
plesiomorphic.”

No. These two clades are in-group taxa in the LRT, not out-group taxa.

“2) The common ancestor of Amniota was fenestrated and that fenestra is the single lateral temporal fenestra of Synapsida and the lower temporal fenestra (LTF) of most reptiles.”

No. Synapsid reptile/amniote ancestors lacked temporal fenestration in the LRT.

“3) ‘Parareptiles’ are polyphyletic and spread along the reptile stem, with the ‘anapsid’ skulls seen in multiple clades representing some of the first of many modifications to the ancestral amniote fenestration.”

Yes. The LRT confirms this hyporthesis.

“4) The evolution of a second, upper temporal fenestra in early reptiles (diapsid fenestration pattern) possibly occurred independently in at least two or three clades; the most important being that the diapsid condition of the late Carboniferous araeoscelidean
Petrolacosaurus is unlikely to be homologous with the diapsid condition of later
neodiapsids like Youngina and the crown group.”

In the LRT Araeoscelids and Youngina are closely related diapsids. Unrelated lepidosaurs also have a diapsid skull architecture.

Figure 1. Drepanosaurus featuring fused finger phalanges and a super claw — among several other odd traits. ” data-image-caption=”

Figure 1. Drepanosaurus featuring fused finger phalanges and a super claw — among several other odd traits.

” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/01/drepanosaurus.jpg?w=295″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/01/drepanosaurus.jpg?w=584″ class=”size-full wp-image-21566″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/01/drepanosaurus.jpg” alt=”Figure 1. Drepanosaurus featuring fused finger phalanges and a super claw — among several other odd traits.” width=”584″ height=”593″ />

Figure 1. Drepanosaurus featuring fused finger phalanges and a super claw — among several other odd traits. This is the type specimen, not the new fiddler crab specimen.

Pritchard AC et al: Extreme left-right asymmetry in the forelimb of a drepanosaur (Diapsida, Drepanosauromorpha) from the Upper Triassic of Utah.

“Drepanosaurs are an enigmatic group of diapsid reptiles…”

Drepanosaurs are not enigmatic in the LRT. They are lepidosaurs close to the origin of lepidosaurs.

“Drepanosaurus, possess a unique forelimb with hyperelongated carpals and a relatively
massive second manual digit and accompanying ungual.”

That interpretation comes from misidentification of the elbow sesamoid, tiny in other drepanosaurs, as a displaced ulna. Details here.

“Here were report on an articulated skeleton (BYU 21952) of a Drepanosaurus-like taxon
… that exhibits extreme left-right asymmetry in the morphology and proportions of its forelimb elements. Its right humerus, ulna, and proximal carpals are markedly more robust
than those of the left while the right ulna, proximal carpals, and second manual
phalanx are also absolutely longer. Most remarkably, the right second manual ungual
is twice as long proximodistally and over three times as tall dorsoventrally relative to its opposite.”

I’m think of a fiddler crab as an analog? The authors do not compare to the symmetrical European Drepanosaurus. Was the larger limb comparable to or much larger than the European elements? Or was the smaller limb diminutive by comparison?

“Multiple drepanosaur skeletons are known from the Saints & Sinners locality, but not all
preserve both forelimbs nor do they exhibit the extreme asymmetry of BYU 21952…this level of asymmetry is not unique to this individual.”

So individual variation? Were the specimens associated? Or isolated?

Perpetuating the Drepanosaurus elbow myth: Pritchard et al. 2016

Prothero D et al: Systematics of the Late Oligocene-Miocene oreodonts (Mammalia: Artiodactyla: Merycoidodontidae)
“their taxonomy has been a chaotic mess, largely due to a series of 8 monographs published between 1940 and 1968. This work included typological oversplitting and inability to recognize differences due to post-mortem deformation”

In the LRT oreodonts evolved to become hippos, desmostylians, mysticetes, pigs, camels, chailcotheres, elephants, horses and rhinos and oreodonts evolved from basal primates. So, more of a grade, less of a clade. Outgroups need to be considered.

“They also became more disparate and distinctive, with small gracile running forms (Merychyus) and short-legged tapir-like forms with retracted nasals that suggest the presence of a short proboscis (Promerycochoerus, Brachycrus, and Merycochoerus).”

“The reason for their extinction is not known, but it does coincide with the expansion of C4
grasslands at 7 Ma, while oreodonts (with their brachydont teeth) might not have been
able to eat gritty grasses.”

Maybe oreodonts didn’t go extinct, but evolved into other forms.
Once an oreodont, always an oredont in phylogenetic analysis.