Xavier Jenkins
@semifossorial.bsky.social
Paleontologist | NSF EAR Postdoctoral Fellow @AMNH | PhD @ ISU | Reptile origins, sensory evolution, and all things Permian 🦎🐢🐊
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 😃
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)
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
Buffa et al.’s paper on the enigmatic Permian reptile 🦎 Galesphyrus and the origin of Neodiapsida is out in the Journal of Systematic Palaeontology! Read the thread 👇 for some important takeaways from our study
@valentinbuffa.bsky.social
#Paleontology #Reptile #Permian
doi.org/10.1080/1477...
@valentinbuffa.bsky.social
#Paleontology #Reptile #Permian
doi.org/10.1080/1477...
November 18, 2025 at 3:51 PM
Buffa et al.’s paper on the enigmatic Permian reptile 🦎 Galesphyrus and the origin of Neodiapsida is out in the Journal of Systematic Palaeontology! Read the thread 👇 for some important takeaways from our study
@valentinbuffa.bsky.social
#Paleontology #Reptile #Permian
doi.org/10.1080/1477...
@valentinbuffa.bsky.social
#Paleontology #Reptile #Permian
doi.org/10.1080/1477...
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!
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...
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.
During my dissertation, my research focused on the Millerettidae, a group that was classically interpreted as 'eosuchians' or close relatives of modern reptiles. Despite this, millerettids have been interpreted as among the basalmost members of Parareptilia for the last few decades 🤔
August 28, 2025 at 12:22 PM
During my dissertation, my research focused on the Millerettidae, a group that was classically interpreted as 'eosuchians' or close relatives of modern reptiles. Despite this, millerettids have been interpreted as among the basalmost members of Parareptilia for the last few decades 🤔
Since the advent of cladistics, reptiles have generally been split into 'eureptiles' and 'parareptiles'. This early dichotomy in the evolution of reptiles has implied long ghost lineages for numerous reptile groups, conflicting with more traditional hypotheses of reptile origins by Romer and Watson
August 28, 2025 at 12:22 PM
Since the advent of cladistics, reptiles have generally been split into 'eureptiles' and 'parareptiles'. This early dichotomy in the evolution of reptiles has implied long ghost lineages for numerous reptile groups, conflicting with more traditional hypotheses of reptile origins by Romer and Watson
It’s finally out!
Our work addressing the origins of reptiles is published in PCJ! peercommunityjournal.org/articles/10....
We use novel info gleaned from the scan data of dozens of stem reptiles to substantially revise our understanding of early reptile evolution #paleontology #herpetology
Our work addressing the origins of reptiles is published in PCJ! peercommunityjournal.org/articles/10....
We use novel info gleaned from the scan data of dozens of stem reptiles to substantially revise our understanding of early reptile evolution #paleontology #herpetology
August 28, 2025 at 12:22 PM
It’s finally out!
Our work addressing the origins of reptiles is published in PCJ! peercommunityjournal.org/articles/10....
We use novel info gleaned from the scan data of dozens of stem reptiles to substantially revise our understanding of early reptile evolution #paleontology #herpetology
Our work addressing the origins of reptiles is published in PCJ! peercommunityjournal.org/articles/10....
We use novel info gleaned from the scan data of dozens of stem reptiles to substantially revise our understanding of early reptile evolution #paleontology #herpetology
Huge thanks to Michel Laurin for his recommendation of my work on reptile origins in PCI Paleontology! First of many works to come (:
Also thanks to Valentin Buffa, David Majanović, and others for their reviews (:
paleo.peercommunityin.org/articles/rec...
Also thanks to Valentin Buffa, David Majanović, and others for their reviews (:
paleo.peercommunityin.org/articles/rec...
August 22, 2025 at 1:33 PM
Huge thanks to Michel Laurin for his recommendation of my work on reptile origins in PCI Paleontology! First of many works to come (:
Also thanks to Valentin Buffa, David Majanović, and others for their reviews (:
paleo.peercommunityin.org/articles/rec...
Also thanks to Valentin Buffa, David Majanović, and others for their reviews (:
paleo.peercommunityin.org/articles/rec...
Cladistic analysis demonstrates that Amenoyengi forms a group with other late-surving and small-bodied moradisaurines. Was there a trend towards smaller body-size late in captorhinid evolution, or are there other biogeographical variables at play? #Captorhinidae #captorhinid
August 7, 2025 at 5:13 PM
Cladistic analysis demonstrates that Amenoyengi forms a group with other late-surving and small-bodied moradisaurines. Was there a trend towards smaller body-size late in captorhinid evolution, or are there other biogeographical variables at play? #Captorhinidae #captorhinid
Collected in the 1960s, this specimen was interpreted as an unnamed species of Captorhinus (an older taxon from North America) for decades. CT-scanning at Wits University has revealed the presence of multiple rows of dentition similar to moradisaurines, including those from Niger and India.
August 7, 2025 at 5:13 PM
Collected in the 1960s, this specimen was interpreted as an unnamed species of Captorhinus (an older taxon from North America) for decades. CT-scanning at Wits University has revealed the presence of multiple rows of dentition similar to moradisaurines, including those from Niger and India.
Now introducing Amenoyengi mpunduensis ('many-tooth from Mpundu'), a small moradisaurine captorhinid from the late Permian of Zambia with multiple rows of teeth! #Permian #Paleontology 😄
www.tandfonline.com/doi/full/10....
www.tandfonline.com/doi/full/10....
August 7, 2025 at 5:13 PM
Now introducing Amenoyengi mpunduensis ('many-tooth from Mpundu'), a small moradisaurine captorhinid from the late Permian of Zambia with multiple rows of teeth! #Permian #Paleontology 😄
www.tandfonline.com/doi/full/10....
www.tandfonline.com/doi/full/10....
Successfully passed my dissertation defense here at ISU! These past five years have been amazing. Fell in love with research, started my family with @thezoiejenkins.bsky.social , and couldn’t have asked for a better advisor in @gondwannabe.bsky.social #Dissertation #PhD
April 18, 2025 at 4:05 PM
Successfully passed my dissertation defense here at ISU! These past five years have been amazing. Fell in love with research, started my family with @thezoiejenkins.bsky.social , and couldn’t have asked for a better advisor in @gondwannabe.bsky.social #Dissertation #PhD
Gemini is using Pterosaur Heresies as one of it's sources now. Extremely concerning...
March 26, 2025 at 2:25 AM
Gemini is using Pterosaur Heresies as one of it's sources now. Extremely concerning...
And our amazing artwork of Milleretta, brought to life by
@serpenillus.bsky.social
😀 #Permian #Fossil #Reptile #Paleontology
@serpenillus.bsky.social
😀 #Permian #Fossil #Reptile #Paleontology
March 4, 2025 at 7:46 PM
And our amazing artwork of Milleretta, brought to life by
@serpenillus.bsky.social
😀 #Permian #Fossil #Reptile #Paleontology
@serpenillus.bsky.social
😀 #Permian #Fossil #Reptile #Paleontology
By this point you hopefully know that 1) Milleretta is cool and 2) I love braincases. Both of these facts combine into one when we look at the inner ear of this taxon, which is surprisingly derived. Large, arcing semicircular canals and a larger lagena than many early amniotes.
March 4, 2025 at 12:13 PM
By this point you hopefully know that 1) Milleretta is cool and 2) I love braincases. Both of these facts combine into one when we look at the inner ear of this taxon, which is surprisingly derived. Large, arcing semicircular canals and a larger lagena than many early amniotes.
Like other millerettids, there is a tympanic fossa shared by the quadrate, quadratojugal, and squamosal 🤔
The stapes is robust, but lacks features present in earlier-diverging reptiles such as a dorsal process. It also does not serve as a brace of the skull, but rather ends freely
The stapes is robust, but lacks features present in earlier-diverging reptiles such as a dorsal process. It also does not serve as a brace of the skull, but rather ends freely
March 4, 2025 at 12:13 PM
Like other millerettids, there is a tympanic fossa shared by the quadrate, quadratojugal, and squamosal 🤔
The stapes is robust, but lacks features present in earlier-diverging reptiles such as a dorsal process. It also does not serve as a brace of the skull, but rather ends freely
The stapes is robust, but lacks features present in earlier-diverging reptiles such as a dorsal process. It also does not serve as a brace of the skull, but rather ends freely
This is achieved by a combination of the development of the posterior process of the jugal and the ventral flange of the parietal, but also other elements.
In juveniles, the postorbital is shorter and does not contact the supratemporal.
In juveniles, the postorbital is shorter and does not contact the supratemporal.
March 4, 2025 at 12:13 PM
This is achieved by a combination of the development of the posterior process of the jugal and the ventral flange of the parietal, but also other elements.
In juveniles, the postorbital is shorter and does not contact the supratemporal.
In juveniles, the postorbital is shorter and does not contact the supratemporal.
Milleretta also closes a lower temporal fenestra AND a ‘gap’ in the region of the Neodiapsid upper temporal fenestra through ontogeny. This latter feature is diagnostic for all millerettids.
I don’t think that this gap actually represents a UTF, but that Permian reptile skulls are a bit nuanced
I don’t think that this gap actually represents a UTF, but that Permian reptile skulls are a bit nuanced
March 4, 2025 at 12:13 PM
Milleretta also closes a lower temporal fenestra AND a ‘gap’ in the region of the Neodiapsid upper temporal fenestra through ontogeny. This latter feature is diagnostic for all millerettids.
I don’t think that this gap actually represents a UTF, but that Permian reptile skulls are a bit nuanced
I don’t think that this gap actually represents a UTF, but that Permian reptile skulls are a bit nuanced