A Re-Description of 'Mycterosaurus' smithae, an Early Permian Eothyridid, and Its Impact on the Phylogeny of Pelycosaurian-Grade Synapsids (original) (raw)
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Royal Society Open Science, 2019
Varanopids are a basal clade of small-to medium-sized nontherapsid synapsids, whose range extends from the late Pennsylvanian to the late middle Permian, and are found in North America, Russia, Europe and South Africa. The greatest varanopid diversity is observed at the fossiliferous cave deposits near Richards Spur, Oklahoma, well known for the preservation of a complex early Permian upland community. Two previously described varanopids, Mycterosaurus and Varanops, are known only from fragmentary disarticulated material at Richards Spur. A third putative varanopid, Basicranodon fortsillensis, represented by a partial parasphenoid, has been synonymized with Mycterosaurus longiceps. This study reports on a new varanopid taxon, represented by substantially more complete material, including three nearly complete skulls. Such comprehensive cranial material allows for a detailed study of the taxon and its relationship to other varanopids. This new varanopid bears great morphological similarity to Mesenosaurus romeri from the middle Permian Mezen River Basin of northern Russia. Phylogenetic analysis recovers a sister relationship between this taxon and Me. romeri. This relationship, in conjunction with a detailed morphological comparison, supports the placement of this taxon within Mesenosaurus, as a new species, Me. efremovi. These results reveal an unexpected extension of the geographical and temporal range of Mesenosaurus, contributing to our understanding of varanopid dispersal. The extended persistence of this basal clade of predatory synapsids, underscored by the apparent evolutionary stasis of this genus, is unusual among Palaeozoic tetrapods.
On the Affinities ofTetraceratops insignis, an Early Permian Synapsid
Acta Palaeontologica Polonica, 2011
The affinities of the Early Permian synapsid Tetraceratops insignis have been reevaluated several times since the early 20 th century, being considered as an eothyridid, a sphenacodontid, or a therapsid. This controversy continues into the 21 st century, with recently raised doubts about the interpretation of Tetraceratops as the oldest known therapsid, a hypothesis supported by the only redescription of this fossil in the second half of the 20 th century. Our study examines the arguments proposed to refute therapsid affinities, and concludes that Tetraceratops indeed is the sister−group of all other known therapsids. The most recently published phylogenetic data matrix that includes Tetraceratops fails to confirm its therapsid affinities. However, adding seven characters to that matrix leads to the conclusion that Tetraceratops is the basal−most and oldest therapsid. The recent suggestion of a Laurasian origin of therapsids appears poorly supported; too few data are available on the distribution of Permian synapsids to settle this question.
PeerJ
The fossil record of caseids, a clade of faunivorous to large herbivorous Permian synapsids, is unusual in having a poorly documented history. Although Kungurian caseids are common in the well-known continental deposits of North America, and the fossil record of the group extends into the middle Permian (Guadalupian), with the presence of the large caseid Ennatosaurus in the Mezen Basin faunal assemblage, only two other occurrences are known in older Permian age sediments. One is an undescribed caseid from the Bromacker Quarry in Germany, and the second is Oromycter from the lower Permian of Richards Spur, Oklahoma. The former is known from several articulated skeletons, but the latter is known only from a handful of skeletal elements, including elements of the snout and lower jaw, some phalanges, and a few vertebrae. Here the fragmentary tooth bearing elements and dorsal vertebrae of another small caseid from Richards Spur are described, with a discussion of its significance in the...
Canadian Journal of Earth Sciences, 2007
Morphological features of the terminal phalanges of extinct tetrapods can be used to infer whether or not keratinous claws were present even though these structures are not preserved in the fossil record. Such features as dense vascularization grooves and foramina, and a general claw-like morphology, are present in some of the earliest fully terrestrial tetrapods, the Permo-Carboniferous synapsids. Early synapsids are represented by a rich fossil record that preserves the detailed anatomy of the terminal phalanges and allows for an examination of the early evolution of these structures in a well-resolved phylogenetic context. The pattern of change in the morphology of the terminal phalanges of five basal synapsids, Cotylorhynchus romeri, Varanops sp., Edaphosaurus boanerges, Haptodus garnettensis, and Dimetrodon limbatus, reveals a clear trend from a broad, flat, and spatulate morphology in the basal taxa to a tall, narrow, and curved structure. This trend in overall shape change does not reflect changes in feeding behaviour. The size and shape of the flexor tubercle appears to be a factor of size and function, rather than possessing a phylogenetically informative signal. The osteological features used to infer the presence of a keratinous sheath in the synapsids are also observed in the non-amniote taxon Diadectes absitus. This indicates that claws were not an amniote innovation and that they instead originated somewhere outside the crown group Amniota.
A reevaluation of the enigmatic Permian synapsid Watongia and of its stratigraphic significance
Canadian Journal of Earth Sciences, 2004
The enigmatic synapsid Watongia, initially described on the basis of fragmentary remains from the Chickasha Formation of Oklahoma as an early therapsid (a gorgonopsian), is redescribed and is shown to represent the largest known varanopid synapsid. Its assignment to the Varanodontinae (Varanopidae: Synapsida) is supported by several diagnostic features, including a strongly recurved marginal dentition with both posterior and anterior, unserrated, cutting edges, quadratojugal with two discrete superficial rami, a large lateral tuberosity on the postorbital, short, deep excavations on the neural arches, and a broad, short radiale. The presence in Watongia of a posterolateral process of the frontal precludes therapsid or sphenacodontid affinities. The previously described preparietal that provided the strongest evidence of therapsid affinities for Watongia is shown to be based on misinterpreted skull fragments that were incorrectly assembled. The presence of a varanopid in the Chickasha Formation is consistent with a Guadalupian age (Middle Permian), and in the absence of large sphenacodontids and therapsids, Watongia was probably the top predator of its terrestrial vertebrate community.
Frontiers in Earth Science, 2022
The detailed description of the cranial anatomy of Cotylorhynchus romeri, a very large caseid synapsid from the lower Permian Hennessey Formation of Oklahoma, uncovered several potential autapomorphies, including parietal-postorbital contact greatly reduced by broad anterior process of supratemporal; the postparietals are transversely broad and contact the supratemporals laterally; the quadratojugal has a pennant-like occipital process; the stapes has a short shaft and a ventral process that abuts against the palate; the bulbous marginal dentition narrows distally and carries three small denticles; the vomer has three large teeth along its medial edge; parasphenoidal dentition is present; and the surangular overlaps the posterodorsal tip of the dentary and excludes it from the coronoid eminence. Owing to lack of comparative cranial material in most large caseids, the evolutionary history of these autapomorphies remains ambiguous because they cannot be determined in the closest relat...
PalZ, 2018
A new fossil amniote from the Fossil Forest of Chemnitz (Sakmarian-Artinskian transition, Germany) is described as Ascen-donanus nestleri gen. et sp. nov., based on five articulated skeletons with integumentary preservation. The slender animals exhibit a generalistic, lizard-like morphology. However, their synapsid temporal fenestration, ventrally ridged centra and enlarged iliac blades indicate a pelycosaur-grade affiliation. Using a renewed data set for certain early amniotes with a similar typology found Ascendonanus to be a basal varanopid synapsid. This is the first evidence of a varanopid from Saxony and the third from Central Europe, as well as the smallest varanopid at all. Its greatly elongated trunk, enlarged autopodia and strongly curved unguals, along with taphonomical observations, imply an arboreal lifestyle in a dense forest habitat until the whole ecosystem was buried under volcanic deposits. Ascendonanus greatly increases the knowledge on rare basal vara-nopids; it also reveals a so far unexpected ecotype of early synapsids. Its integumentary structures present the first detailed and soft tissue skin preservation of any Paleozoic synapsid. Further systematic results suggest a varanodontine position for Mycterosaurus, the monophyly of South African varanopids including Anningia and the distinction of a skeletal aggregation previously assigned to Heleosaurus, now renamed as Microvaranops parentis gen. et sp. nov. Kurzfassung Basierend auf fünf artikulierten Skeletten mit Hauterhaltung wird ein neuer, fossiler Amniot aus dem Versteinerten Wald von Chemnitz (Sakmarium-Artinskium-Grenzbereich, Deutschland) beschrieben als Ascendonanus nestleri gen. et sp. nov. Die schlanken Tiere sind von generalistischer, echsenhafter Gestalt. Demgegenüber zeigen die synapsiden Schläfenfenster, ventral gekantete Zentren und vergrößerte Iliumblätter eine Zugehörigkeit zur Pelycosaurier-Stufe an. Unter Anwendung eines erneuerten Datensatzes für ausgewählte frühe Amnioten ähnlicher Typologie wird Ascendonanus zu basalen Varano-piden gestellt. Damit liegt der erste Nachweis eines Varanopiden aus Sachsen und der dritte aus Mitteleuropa vor, zudem der kleinste Varanopide überhaupt. Sein besonders verlängerter Rumpf, vergrößerte Autopodien und stark gekrümmte Krallen sowie taphonomische Beobachtungen legen eine arboreale Lebensweise inmitten eines dichten Waldhabitats nahe, bis das gesamte Ökosystem von vulkanischen Ablagerungen verschüttet wurde. Ascendonanus erweitert die Kenntnis der seltenen basalen Varanopiden enorm, zumal er einen bei frühen Synapsiden bisher unerwarteten Ökotyp aufdeckt. Die Integu-mentstrukturen stellen die ersten detaillierten und durch Weichteile erhaltenen Hautfunde aller paläozoischen Synapsiden dar. Weitergehende systematische Ergebnisse deuten an: eine varanodontine Position für Mycterosaurus, die Monophylie Handling Editor: Jörg Fröbisch. Electronic supplementary material The online version of this article (https ://doi.
The carpus and tarsus of the sphenacodontid synapsid Sphenacodon ferox are described in detail for the first time on the basis of nearly complete, loosely articulated examples from an incomplete, partially articulated skeleton from the Lower Permian El Cobre Canyon Formation of the Cutler Group of north-central New Mexico. On the one hand, the carpus and tarsus of S. ferox are compared to those of the more derived Dimetrodon and only member of Sphenacodontidae in which these structures are otherwise known adequately, and, on the other, to Haptodus, the sole member of the sister taxon of Sphenacodontoidea (Sphenacodontidae plus Therapsida). In order to recognize possible morphological trends in the carpus and tarsus within the combined clades of Haptodus and Sphenacodontidae, members of the sister clades Ophiacodontidae and Varanopseidae are utilized for outgroup comparison.