Xavier Jenkins
@semifossorial.bsky.social
Paleontologist | NSF EAR Postdoctoral Fellow @AMNH | PhD @ ISU | Reptile origins, sensory evolution, and all things Permian 🦎🐢🐊
Check the paper out above👆 to learn more!!
Keep an eye out for future work by @valentinbuffa.bsky.social, myself, and others on early reptiles…. 🦎🐍🐢
Some exciting stuff inbound! (:
Keep an eye out for future work by @valentinbuffa.bsky.social, myself, and others on early reptiles…. 🦎🐍🐢
Some exciting stuff inbound! (:
November 18, 2025 at 3:51 PM
Check the paper out above👆 to learn more!!
Keep an eye out for future work by @valentinbuffa.bsky.social, myself, and others on early reptiles…. 🦎🐍🐢
Some exciting stuff inbound! (:
Keep an eye out for future work by @valentinbuffa.bsky.social, myself, and others on early reptiles…. 🦎🐍🐢
Some exciting stuff inbound! (:
Our postcranial observations, specifically on the foot, suggests that many features of the modern reptile hindlimb are actually present in their closest fossil relatives!
You heard it folks: milleretids are *also* postcranially very neodiapsid-like 😃
You heard it folks: milleretids are *also* postcranially very neodiapsid-like 😃
November 18, 2025 at 3:51 PM
Our postcranial observations, specifically on the foot, suggests that many features of the modern reptile hindlimb are actually present in their closest fossil relatives!
You heard it folks: milleretids are *also* postcranially very neodiapsid-like 😃
You heard it folks: milleretids are *also* postcranially very neodiapsid-like 😃
The relationship of Galesphyrus relative to other derived stem reptiles, including parapleurotans, suggests than neodiapsids must have originated sometime in the middle Permian, and certainly by the latest Capitanian. 🔨
November 18, 2025 at 3:51 PM
The relationship of Galesphyrus relative to other derived stem reptiles, including parapleurotans, suggests than neodiapsids must have originated sometime in the middle Permian, and certainly by the latest Capitanian. 🔨
Incorporating these observations into an expanded phylogenetic dataset, Buffa et al. place Galesphyrus as the sister to Millerettidae + Neodiapsida, a group I recently named Parapleurota (‘Clade P’ below)
November 18, 2025 at 3:51 PM
Incorporating these observations into an expanded phylogenetic dataset, Buffa et al. place Galesphyrus as the sister to Millerettidae + Neodiapsida, a group I recently named Parapleurota (‘Clade P’ below)
When Valentin studied Galesphyrus specimens, he noted similarities in the postcranial skeleton of millerettids and neodiapsids. Interestingly, many of these features were absent in Galesphyrus. 👀
November 18, 2025 at 3:51 PM
When Valentin studied Galesphyrus specimens, he noted similarities in the postcranial skeleton of millerettids and neodiapsids. Interestingly, many of these features were absent in Galesphyrus. 👀
But then I met @valentinbuffa.bsky.social and found out he INDEPENDENTLY
came to same conclusion using POSTCRANIAL EVIDENCE! 🤯
This is exciting, because not only did I feel like it supported some of my hypotheses, but it sampled an anatomical region (the hindlimb) that I largely did not study 📚
came to same conclusion using POSTCRANIAL EVIDENCE! 🤯
This is exciting, because not only did I feel like it supported some of my hypotheses, but it sampled an anatomical region (the hindlimb) that I largely did not study 📚
November 18, 2025 at 3:51 PM
But then I met @valentinbuffa.bsky.social and found out he INDEPENDENTLY
came to same conclusion using POSTCRANIAL EVIDENCE! 🤯
This is exciting, because not only did I feel like it supported some of my hypotheses, but it sampled an anatomical region (the hindlimb) that I largely did not study 📚
came to same conclusion using POSTCRANIAL EVIDENCE! 🤯
This is exciting, because not only did I feel like it supported some of my hypotheses, but it sampled an anatomical region (the hindlimb) that I largely did not study 📚
During my graduate research, I argued that millerettids were indeed close relatives of crown reptiles and neodiapsids, primarily based on neurocranial evidence. I also showed that ‘Parareptilia’ is a polyphlyetic assemblage of unrelated stem reptiles
peercommunityjournal.org/articles/10....
peercommunityjournal.org/articles/10....
Evolutionary assembly of crown reptile anatomy clarified by late Paleozoic relatives of Neodiapsida
peercommunityjournal.org
November 18, 2025 at 3:51 PM
During my graduate research, I argued that millerettids were indeed close relatives of crown reptiles and neodiapsids, primarily based on neurocranial evidence. I also showed that ‘Parareptilia’ is a polyphlyetic assemblage of unrelated stem reptiles
peercommunityjournal.org/articles/10....
peercommunityjournal.org/articles/10....
Millerettids, as you may know by now, are a group of fossil stem reptiles from the Permian of South Africa. For much of their history, they were implicated in crown reptile origins. However, with the advent of cladistics they were placed among the #Parareptilia
November 18, 2025 at 3:51 PM
Millerettids, as you may know by now, are a group of fossil stem reptiles from the Permian of South Africa. For much of their history, they were implicated in crown reptile origins. However, with the advent of cladistics they were placed among the #Parareptilia
Carroll (1976) solidified Galesphyrus’s position among neodiapsids, but later observed that many aspects of the hindlimb were millerettid-like, and similar to the millerettid Broomia perplexa
November 18, 2025 at 3:51 PM
Carroll (1976) solidified Galesphyrus’s position among neodiapsids, but later observed that many aspects of the hindlimb were millerettid-like, and similar to the millerettid Broomia perplexa
Galesphyrus has a complicated history. Originally, Broom (1914) interpreted it as a therapsid or a varanopid (both clades that are likely total-group mammals), but later most subsequent studies recognized it as a close relative of Youngina and eosuchians.
November 18, 2025 at 3:51 PM
Galesphyrus has a complicated history. Originally, Broom (1914) interpreted it as a therapsid or a varanopid (both clades that are likely total-group mammals), but later most subsequent studies recognized it as a close relative of Youngina and eosuchians.
Reposted by Xavier Jenkins
DR. TSOGTBAATAR FUNDRAISER: gofund.me/c8d8d1ab7
Donate to Help Dr. Tsogtbaatar, Icon of Mongolian Paleontology, organized by Lindsay Zanno
Renowned Mongolian paleontologist Dr. Khishigjav Tsogtbaatar is fig… Lindsay Zanno needs your support for Help Dr. Tsogtbaatar, Icon of Mongolian Paleontology
gofund.me
October 8, 2025 at 1:19 AM
DR. TSOGTBAATAR FUNDRAISER: gofund.me/c8d8d1ab7
Keep an eye out for an incoming paper by @valentinbuffa.bsky.social that better investigates the postcranial evolution of these reptiles and their relatives (:
August 28, 2025 at 12:23 PM
Keep an eye out for an incoming paper by @valentinbuffa.bsky.social that better investigates the postcranial evolution of these reptiles and their relatives (:
So what's next? I am expanding this phylogenetic dataset to better tackle the explosive radiation of early neodiapsids in the late Permian and crown reptiles in the Triassic. I also hope to detail some of our observations on synapsid evolution soon!
And, it goes without saying...more descriptions!
And, it goes without saying...more descriptions!
August 28, 2025 at 12:23 PM
So what's next? I am expanding this phylogenetic dataset to better tackle the explosive radiation of early neodiapsids in the late Permian and crown reptiles in the Triassic. I also hope to detail some of our observations on synapsid evolution soon!
And, it goes without saying...more descriptions!
And, it goes without saying...more descriptions!
Specifically, by placing 'the earliest reptile' Hylonomus on the amniote stem and removing a ~50 million and ~30 million year ghost lineage for Millerettidae and Neodiapsida, we greatly improve the stratigraphic record of early reptiles and amniotes more broadly!
August 28, 2025 at 12:23 PM
Specifically, by placing 'the earliest reptile' Hylonomus on the amniote stem and removing a ~50 million and ~30 million year ghost lineage for Millerettidae and Neodiapsida, we greatly improve the stratigraphic record of early reptiles and amniotes more broadly!
We found that this topology greatly improves the fit of the reptile evolutionary tree to the stratigraphic record by at least 27% compared to studies finding a 'Eureptilia' or 'Parareptilia'...
August 28, 2025 at 12:23 PM
We found that this topology greatly improves the fit of the reptile evolutionary tree to the stratigraphic record by at least 27% compared to studies finding a 'Eureptilia' or 'Parareptilia'...
Beyond anatomical and statistical support, how does our phylogenetic hypothesis match the fossil record for early reptiles? To test this, we performed a series of stratigraphic fit analyses...
August 28, 2025 at 12:22 PM
Beyond anatomical and statistical support, how does our phylogenetic hypothesis match the fossil record for early reptiles? To test this, we performed a series of stratigraphic fit analyses...
With our new data, millerettids are most parsimoniously interpreted as close relatives of neodiapsids even when the monophyly of clades such as 'Diapsida', 'Eureptilia', and 'Parareptilia' are enforced...
August 28, 2025 at 12:22 PM
With our new data, millerettids are most parsimoniously interpreted as close relatives of neodiapsids even when the monophyly of clades such as 'Diapsida', 'Eureptilia', and 'Parareptilia' are enforced...
We (and our reviewers) were also genuinely curious as to how robust our phylogenetic hypothesis for Millerettidae was compared to traditional frameworks of early reptile evolution, so we performed a series of constraint analyses...
August 28, 2025 at 12:22 PM
We (and our reviewers) were also genuinely curious as to how robust our phylogenetic hypothesis for Millerettidae was compared to traditional frameworks of early reptile evolution, so we performed a series of constraint analyses...
Millerettids and neodiapsids also share several derived features involved in the reorganization of the gastralia and caudofemoralis musculature. Parapleurotans are the only Paleozoic reptiles with a midline gastral element and fused, laterally directed caudal ribs, for example.
August 28, 2025 at 12:22 PM
Millerettids and neodiapsids also share several derived features involved in the reorganization of the gastralia and caudofemoralis musculature. Parapleurotans are the only Paleozoic reptiles with a midline gastral element and fused, laterally directed caudal ribs, for example.
Our ancestral state reconstruction supports a middle Permian origin of the reptile tympanum, Future work on non-saurian neodiapsids will shed light on this question, but I'll note that a tympanum was recently described in tangasaurids....
August 28, 2025 at 12:22 PM
Our ancestral state reconstruction supports a middle Permian origin of the reptile tympanum, Future work on non-saurian neodiapsids will shed light on this question, but I'll note that a tympanum was recently described in tangasaurids....
In fact, we suggest that the tympanum of modern reptiles originated in the common ancestor of Parapleurota in the middle Permian. Excitingly, recent developmental work by Bronzati et al. has shown that the modern reptile tympanum was present in their common ancestor, congruent with this hypothesis
August 28, 2025 at 12:22 PM
In fact, we suggest that the tympanum of modern reptiles originated in the common ancestor of Parapleurota in the middle Permian. Excitingly, recent developmental work by Bronzati et al. has shown that the modern reptile tympanum was present in their common ancestor, congruent with this hypothesis
We name this clade Parapleurota, which is currently supported by 21 unambiguous synapomorphies across the skeleton. These include numerous features related to a reorganization of the middle ear and cranial nerves.....
August 28, 2025 at 12:22 PM
We name this clade Parapleurota, which is currently supported by 21 unambiguous synapomorphies across the skeleton. These include numerous features related to a reorganization of the middle ear and cranial nerves.....
When these observations were incorporated into an expanded phylogenetic analysis (647 characters, the largest such study on early reptile origins), we find Millerettidae in a crownward position as sister to Neodiapsida, a group of reptiles which includes modern reptiles and their closest relatives.
August 28, 2025 at 12:22 PM
When these observations were incorporated into an expanded phylogenetic analysis (647 characters, the largest such study on early reptile origins), we find Millerettidae in a crownward position as sister to Neodiapsida, a group of reptiles which includes modern reptiles and their closest relatives.
Perhaps not so surprisingly, these 'eureptiles' were generally considered stem amniotes in pre-cladistic works. More specifically, they were thought to have 'given rise' or were 'directly ancestral' to all other amniote. This includes Hylonomus, the putative 'earliest reptile'...
August 28, 2025 at 12:22 PM
Perhaps not so surprisingly, these 'eureptiles' were generally considered stem amniotes in pre-cladistic works. More specifically, they were thought to have 'given rise' or were 'directly ancestral' to all other amniote. This includes Hylonomus, the putative 'earliest reptile'...