SVP 2025 abstracts of interest 7
It’s SVP abstracts season!
Now deeper into the second half of the bunch with part 7 of 10.
Figure 6. Dorsal and ventral views of Panderichthys and several basal tetrapods demonstrating the low, flat skulls and bodies with small limbs and relatively straight ribs.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/04/panderichthys_trypanognathus_ventral588.jpg?w=82″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/04/panderichthys_trypanognathus_ventral588.jpg?w=279″ class=”size-full wp-image-44021″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/04/panderichthys_trypanognathus_ventral588.jpg” alt=”Figure 6. Dorsal and ventral views of Panderichthys and several basal tetrapods demonstrating the low, flat skulls and bodies with small limbs and relatively straight ribs.” width=”584″ height=”2145″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/04/panderichthys_trypanognathus_ventral588.jpg?w=584&h=2145 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/04/panderichthys_trypanognathus_ventral588.jpg?w=41&h=150 41w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/04/panderichthys_trypanognathus_ventral588.jpg?w=82&h=300 82w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2020/04/panderichthys_trypanognathus_ventral588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 1. Dorsal and ventral views of Panderichthys and several basal tetrapods demonstrating the low, flat skulls and bodies with small limbs and relatively straight ribs. Note the phylogeneetic reduction at the origin of small limbs from small fins.
New Tiktaalik roseae material reveals locomotor innovation in the water-to-land transition
Hillan (p302)
“A persistent question remains: how might an animal begin to experiment with substrate-based locomotion before it has evolved the musculoskeletal structures necessary for appendage-driven propulsion?”
See figure 1 for a phylogenetic explanation using taxa at the transition. Tiktaalik is not at the transition in the large reptile tree (LRT, 2340 taxa).
“I propose that in this species, the ancestral locomotor mode of axial bending driven swimming transitioned into axial bending-driven walking, with limbs coopted to stabilize rather than to propel.”
That was proposed before in 2021. Good to get confirmation. Look at Panderichthys and Trypanognathus (Figs 1, 2) for the LRT fin-to-finger transition. Four fingers is primitive. The fins then limbs are not large enough to elevate the belly off the substrate, only to stabilize the already flattened body.
Figure 1. From Boisert et al. 2008, colors added. This is their ordering for the evolution of manual digits.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/panderichthys_digitsb-588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/panderichthys_digitsb-588.jpg?w=584″ class=”size-full wp-image-95279″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/panderichthys_digitsb-588.jpg” alt=”Figure 1. From Boisert et al. 2008, colors added. This is their ordering for the evolution of manual digits. ” width=”584″ height=”328″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/panderichthys_digitsb-588.jpg?w=584&h=328 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/panderichthys_digitsb-588.jpg?w=150&h=84 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/panderichthys_digitsb-588.jpg?w=300&h=168 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/11/panderichthys_digitsb-588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 2. From Boisert et al. 2008, colors added. This is their ordering for the evolution of manual digits.
“The results suggest a previously unrecognized range of morphological form and locomotor experimentation across the tetrapod stem.”
If Emily Hillan thought this was ‘previously unrecognized’ I would have to blame her education, textbooks and professors. This was online when late-surviving Trypanognathus (Figs 1,2) entered the LRT in 2019 as ‘the most primitive fingers and toes’ and/or when Pholidogaster entered the LRT in 2017 in a similar fashion and perhaps by convergence.
Figure 1. Large Sclerocormus and its much smaller sister, Cartorhynchus. These nest with basal sauropterygians, not ichthyosauriforms.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg?w=584″ class=”size-full wp-image-22862″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg” alt=”Figure 1. Large Sclerocormus and its much smaller sister, Cartorhynchus. These nest with basal sauropterygians, not ichthyosauriforms.” width=”584″ height=”274″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg?w=584&h=274 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg?w=150&h=70 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg?w=300&h=141 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg?w=768&h=360 768w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2016/05/sclerocormus_recon1000.jpg 1000w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 3. Large Sclerocormus and its much smaller sister, Cartorhynchus. These nest with basal sauropterygians, not ichthyosauriforms.
New Sclerocormus specimens confirming differences in the dentition between Nasorostra and Omphalosauridae
Jiang et al (p 327)
“The Early Triassic basal ichthyosauriform Cartorhynchus and Sclerocormus form the monophyly Nasorostra, which is the sister taxon to Ichthyopterygia.”
Not in the LRT, which nests these two taxa at the base of the Sauropterygia, with Qianxidsaurus. Meanwhile elsewhere in the LRT Permian mesosaurs and thalattosaurs are ichthyosaur outgroups.
“They were unlike any other ichthyosauromorph by their autapomorphically short and pointed snout with rostrally extended nasals and weakly jointed jaw symphysis, enlarged wrist space of forefins, and a long tail while retaining a short trunk.”
Whenever you find yourself writing such a sentence (‘unlike any other’), consider the possibility of being incorrect due to taxon exclusion = cherry-picking taxa = following academic tradition without experimentation = taking the easy way out.
“Unlike Sclerocormus, the teeth of Cartorhynchus are perpendicular to the outer walls of the respective jaw rami and thus horizontally orientated.”
Those horizontal teeth must be tiny.
Figure 2. Cartorhynchus reconstruction in lateral and dorsal views with new lateral view skull and pectoral girdle.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/02/cartorhynchus-recon588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/02/cartorhynchus-recon588.jpg?w=584″ class=”size-full wp-image-35662″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/02/cartorhynchus-recon588.jpg” alt=”Figure 2. Cartorhynchus reconstruction in lateral and dorsal views with new lateral view skull and pectoral girdle.” width=”584″ height=”454″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/02/cartorhynchus-recon588.jpg?w=584&h=454 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/02/cartorhynchus-recon588.jpg?w=150&h=117 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/02/cartorhynchus-recon588.jpg?w=300&h=233 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2019/02/cartorhynchus-recon588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 4. Cartorhynchus reconstruction in lateral and dorsal views with new lateral view skull and pectoral girdle.
“The dentition of Nasorostra partly resembles that of Omphalosaurus.”
The two clades are not quite related in the LRT separated by about five nodes. Build a cladogram so you can be precise. Here is Omphalosaurus.
“Most teeth of Nasorostra are very small, possess a root with only one tooth per tooth position suggesting lateral tooth replacement, and are arranged in multiple rows.”
How small? Millimeter-ish in size? Must be.
Figure 3. The Devonian placodersms, Amazichthys and Millerosteus (not to scale) are compared to the Devonian sharks, Cladoselache and Maghriboselache. Currently Cladoselache does not nest with the other three in the LRT, but that may change.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/01/cladoselache_amazichthys.jpg?w=223″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/01/cladoselache_amazichthys.jpg?w=584″ class=”size-full wp-image-83682″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/01/cladoselache_amazichthys.jpg” alt=”Figure 3. The Devonian placodersms, Amazichthys and Millerosteus (not to scale) are compared to the Devonian sharks, Cladoselache and Maghriboselache. Currently Cladoselache does not nest with the other three in the LRT, but that may change.” width=”584″ height=”787″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/01/cladoselache_amazichthys.jpg?w=584&h=787 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/01/cladoselache_amazichthys.jpg?w=111&h=150 111w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/01/cladoselache_amazichthys.jpg?w=223&h=300 223w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2024/01/cladoselache_amazichthys.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 5. The Devonian placodersms, Amazichthys and Millerosteus (not to scale) are compared to the Devonian sharks, Cladoselache and Maghriboselache. Currently Cladoselache does not nest with the other three in the LRT, but that may change.
The face of the oldest elasmobranch Phoebodus from the Moroccan Devonian
Klug et al (p350)
“Recently published examples from Morocco are the placoderm Alienacanthus and the chondrichthyans Ferromirum, Maghriboselache, and Phoebodus.
In the LRT Alienacanthus is a primitive sea robin. Ferromirum and Maghriboselache are sharrk-like placoderms and Phoebodus remains untested but is considered close to the eel-like extant seven-gilled shark, Chlamydoselachus.
“Newly prepared Famennian (= Late Devonian) materials of Phoebodus saidselachus revealed that this early elasmobranch had several characters shared with modern relatives, such as the slender head with a pointed rostrum and the likely rapid tooth replacement indicated by the subtle size changes between subsequent teeth within one tooth file and the absence of worn teeth retained on the labial side of the jaw cartilages.”
Publiicity
dailymail.co.uk/sciencetech/article-7533231/The-fossil-skeleton-ancient-Phoebodus-shark-found.html
Figure 2. Compare Eudibamus to bolosaurids on the left and diapsids on the right.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/09/bolosaurus-eudibamus3.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/09/bolosaurus-eudibamus3.jpg?w=584″ class=”size-full wp-image-19596″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/09/bolosaurus-eudibamus3.jpg” alt=”Figure 2. Compare Eudibamus to bolosaurids on the left and diapsids on the right.” width=”584″ height=”310″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/09/bolosaurus-eudibamus3.jpg?w=584&h=310 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/09/bolosaurus-eudibamus3.jpg?w=150&h=80 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/09/bolosaurus-eudibamus3.jpg?w=300&h=159 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2011/09/bolosaurus-eudibamus3.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 6. Compare Eudibamus to bolosaurids on the left and diapsids on the right.
Computed tomography (CT) data reveals new insights into the evolution of herbivory in bolosaurian reptiles
MacDougall, Ponstein and Fröbish (p399)
“Primitive bolosaurian taxa, specifically Erpetonyx, exhibit few if any adaptations for herbivory, whereas we observe a cascade of increasing complexity of dental adaptions in more derived taxa, such as Eudibamus, Bolosaurus, and Belebey.”
In the LRT only Bolosaurus and Belebey (Fig 6) are members of the Bolosauridae close to Diadectidae within the Lepidosauromorpha. Meanwhile Erpetonyx (Figs 7, 8) and Eudibamus (Fig 6) are basal members of the Diapsida within the Archosauromorpha.
Figure 2. Erpetonyx in situ.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx_overall_insitu588.jpg?w=130″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx_overall_insitu588.jpg?w=445″ class=”size-full wp-image-64643″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx_overall_insitu588.jpg” alt=”Figure 2. Erpetonyx in situ.” width=”584″ height=”1343″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx_overall_insitu588.jpg?w=584&h=1343 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx_overall_insitu588.jpg?w=65&h=150 65w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx_overall_insitu588.jpg?w=130&h=300 130w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx_overall_insitu588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 7. Erpetonyx in situ.
Figure 1. Skull of Erpetonyx in situ and reconstructed.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx-skull588-2.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx-skull588-2.jpg?w=584″ class=”size-full wp-image-64659″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx-skull588-2.jpg” alt=”Figure 1. Skull of Erpetonyx in situ and reconstructed.” width=”584″ height=”332″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx-skull588-2.jpg?w=584&h=332 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx-skull588-2.jpg?w=150&h=85 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx-skull588-2.jpg?w=300&h=170 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2022/02/erpetonyx-skull588-2.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 8. Skull of Erpetonyx in situ and reconstructed.
The origin and early evolution of amniotes in phylogenetic context: step 2
Marjanovic (p 408)
“So far, all phylogenetic analyses of early limbed vertebrates have either (1) spanned from the origin of limbs to that of Amniota, barely reaching into Amniota; or (2) covered amniote phylogeny and barely reached beyond.”
Like this author it is common to ignore the LRT, which includes taxa from the Ediacaran to the Recent. But you can tell we are thinking along similar lines. Adding taxa is good and discoveries come about when more taxa are in the same tree.
“To test these and other questions, I greatly enlarged my dataset with characters and data from, e.g., the mentioned works, forgotten fossils, and ancient Soviet literature.”
That’s a good start.
“It now spans the range from before the origin of limbs to the origin of neodiapsids.”
Hold off on applying labels until after all the taxa you want are in the matrix and cladogram. The LRT does not recover the clade ‘Neodiapsida’ but instead recovers two unrelated clades with a diapsid skull architecture.
“I find that many characters so far used only for amniote phylogeny are also informative far outside Amniota, and vice versa.”
Confirmed by the LRT which uses nearly the same set of characters for worms, fish, reptiles and humans.
“Current results indicate a long pan-amniote stem (support ~ 15 steps) with diadectomorphs, Opisthodontosaurus, captorhinids including Petrolacosaurus, and various small Carboniferous tetrapods.”
The author has failed to find the basal dichotomy at the first appearance of the amniotic egg with the taxon Silvanerpeton. The LRT does not nest Petrolacosaurus anywhere near captorhinids because the LRT includes far more taxa.
“I also discuss the evolution of costal lung ventilation, the timing of the origin of claws and the origin of Amniota, and the hypothesis of a size squeeze involved in the origin of the amniotic egg.”
Too late. The LRT found all these aspects a decade agp. Let’s see the confirmation, modification or refutation with a similar taxon list.
Figure 2. Agriodontosaurus µCT scans and diagrams from Marke et al 2025 here compared to Gephyrosaurus. DGS colors added or modified here.
” data-medium-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.skull588.jpg?w=300″ data-large-file=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.skull588.jpg?w=584″ class=”size-full wp-image-94451″ src=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.skull588.jpg” alt=”Figure 2. Agriodontosaurus µCT scans and diagrams from Marke et al 2025 here compared to Gephyrosaurus. DGS colors added or modified here.” width=”584″ height=”481″ srcset=”https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.skull588.jpg?w=584&h=481 584w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.skull588.jpg?w=150&h=123 150w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.skull588.jpg?w=300&h=247 300w, https://pterosaurheresies.wordpress.com/wp-content/uploads/2025/09/agriodontosaurus.skull588.jpg 588w” sizes=”(max-width: 584px) 100vw, 584px” />
Figure 9. Agriodontosaurus µCT scans and diagrams from Marke et al 2025 here compared to Gephyrosaurus. DGS colors added or modified here.
Expected and unexpected features of the oldest crown lepidosaur
Marke et al (p409)
“Here we report a reasonably complete skull and skeleton of a definitive rhynchocephalian from the Middle Triassic (Anisian) Helsby Sandstone Formation of Devon, some 3–7 million years older than the oldest currently known lepidosaur.”
Usually abstracts describe future or anticipated publications. This time the specimen was published before the SVP convention.
According to Wikipedia, “The oldest known definitive lepidosaur is the rhynchocephalian Agriodontosaurus from the Helsby Sandstone Formation of the United Kingdom, dating to the upper Anisian stage of the Middle Triassic, approximately 244 to 241.5 million years ago.”
The same set of authors appear to describe this specimen here and before.
Be careful with phylogenetic superlatives like ‘oldest’. In the LRT the last common ancestor of Sphenodon and Iguana is Earliest Permian Tridentinosaurus. It is currently the most primitive and oldest known lepidosaur in the LRT. Related Coelurosauravus is from the Late Permian. Lanthanolania is from the Middle Permian.Saurosternon, Palaeogama and Lacertulus are from the Late Permian.
Source: https://pterosaurheresies.wordpress.com/2025/11/19/svp-2025-abstracts-of-interest-7/
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