Abstracts of interest from Canadian SVP May 1–3, 2026

Wednesday, November 11, 2026 8:01

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Did not know
the Canadians held their own conference back in early May. (I’m often the last to know.) Some abstracts of interest follow. Many deal with hadrosaurids, ceratopsians, tyrannosaurs and mosasaurs, fossil taxa more common in Alberta than elsewhere.

BTW: Today is day one for the worldwide SVP conference in Cleveland, USA, but still no abstract PDF on the Internet, distinct from prior years. Send a PDF if you have one.

The nature of cranial developmental divergence at the base of Galloanserae: combining comparativeontogeny with the avian fossil record. Arnaout et al wrote: “Underlying these distinct adult morphologies is an evolutionary divergence in skull development between Galliformes and Anseriformes, which remains poorly understood.” That’s because in trait analysis (the LRT) these two clades do nest close to one another.

A rare juvenile mosasaur provides potential insights into ontogenetic change within the subfamily Plioplatecarpinae (Squamata, Mosasauridae) Cameron et al wrote, “Due to a lack of juvenile and subadult specimens preserved in the fossil record, very little is known about mosasaur ontogeny.” This one was reduced to bits and pieces discovered in 1974 – 52 years ago. Even so, good to have!

Evolution of early primate vision: insights frompetrosal lobule size in Dryomomys szalayi (late Paleocene, Wyoming) Dixon, Bloch and Silcox wrote, “Dryomomys szalayi is a plesiadapiform primate belonging to the Micromomyidae, a family that branched very early from the primate stem.” In the LRT plesiadapiformes (Fig 1) are not related to primates because they have rodent-like dentition, not the primate standard of incisors, canines, premolar and molars without a large diastema. Plesiadapiformes are closer to multituberculates, rodents and the aye-aye (Daubentonia) in the LRT, all derived from diphyodont marsupials. Not sure why Dixon, Bloch and Silcox are holding on to this outdated hypothesis of interrelationships spoiled by different teeth.

Figure 3. Petaurus and several descendant clades. — Figure 1. Petaurus and several descendant clades.

Secondarily aquatic tetrapod twins: Crassigyrinus and Vancleavea — an example of convergent evolution. Henderson compared these two taxa, but labeled Vancleavea (Fig 2) an early archosauriform when it nests with the thalattosaur, Helveticosaurus (Fig 2), in the LRT. Thereafter he pulls several Larry Martins while explaining the several convergent traits, which is entertaining, but then what? Unfortunately Henderson did not cherry-pick Helveticosaurus for his ‘convergence’ example.

Figure 2. Vancleavea with its sister, Helveticosaurus.

Assessing grasping ability in early bird antecedents, and implications for the origins of avian flight. Senger and Sullivan reported, “The arboreal hypothesis, but not the cursorial one, predicts a high level of manual grasping ability in theropods closely related to birds, because of the pos-tulated use of the forelimbs in climbing. Our results indicate that early birds and non-avian theropods exhibit generally conservative proportions of the manual digits, with no clear trend that would indicate an increase in grasping ability preceding the transition to flight.” BTW, and just for the record, we have living examples of this trait and behavior in juvenile hoatzins (Fig 3).

Figure 3. A selection of pre-bird and bird hands/wings including Haplocheirus, Limusaurus, Velociraptor, Archaeopteryx, Anser, Passer and two versions of the Hoatzin , Opisthocomus, adult and juvenile. Click to enlarge. Not to scale. Note the medial digit of the outlier, Limusaurus, which is a product of neotony, retained from embryonic tissue recapitulating the seven-finger manus of basal tetrapods (figure 3). Note the return of digit 0 fused to the anterior rim of Anser, Passer and the adult Opisthocomus.

The developmental origin of the ornithischian predentary and its derived morphology. Sukkert and Currie reported, “The predentary is traditionally considered a neomorphic element without a precursor observed in the fossil record. This study analyses the ornithischian predentary through thin-section histology, alongside micro- and nano-CT scanning. The sampled predentaries, of distinct ontogenetic stages ranging from embryonic to fully mature, arecompared with originally-produced sections of other osseous tissues in the ornithischian skeleton Our observations through histology and CT scanning instead indicate an intramembranous origin of the predentary.” I also would have used phylogenetic analysis to look at the last common ancestor of all ornithischians (Fig 4), then look for its immediate ancestor.