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Pelycosaurian reptiles from the Middle Pennsylvanian of North America
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... Synapsids rose quickly to prominence within the terrestrial carnivore guild during the first major radiation of terrestrial amniotes in the Late Carboniferous 26 , with basal, 'pelycosaur-grade' synapsids becoming the top terrestrial predators by the early Permian 27,28 . Despite extinction events at the end of the early and middle Permian that eliminated much of their diversity, synapsids maintained a monopoly on large terrestrial carnivore niches to the end of the Palaeozoic, with successive diversifications of therapsids creating rich, new carnivore communities, dominated by biarmosuchians and dinocephalians in the Guadalupian, and then gorgonopsians and therocephalians in the Lopingian 2,29 . ...
... Differences between GG and FG raptorial specialists in MA, areas of muscle attachment, and dentary robusticity (Figs. 1b and 4 and Supplementary Fig. 6) (Fig. 2) illustrate FG optimisation for biting efficiency and power over biting speed 28 . Growing tooth size and shape variation through basal synapsid evolution 42 supports a shift towards more complex jaw use and feeding behaviour associated with tetrapodon-tetrapod predation. ...
... The onset of climatic trends towards greater aridity and seasonality in the Kasimovian saw increasing environmental heterogeneity through the CRC 71,72 . Early amniotes were closely associated with dry, upland environments 28,135 and the spread of drier habitats through the CRC favoured amniotes, likely encouraging their diversification 5,9,42 . The first appearance of tetrapod herbivores during this time made more energy readily available to terrestrial ecosystems by tapping into the productivity of land-based vegetation, pulling tetrapod food chains further inland and spurring terrestrial trophic network complexification 7,76 . ...
Terrestrial ecosystems evolved substantially through the Palaeozoic, especially the Permian, gaining much new complexity, especially among predators. Key among these predators were non-mammalian synapsids. Predator ecomorphology reflect interactions with prey and competitors, which are key controls on carnivore diversity and ecology. Therefore, carnivorous synapsids may offer insight on wider ecological evolution as the first complex, tetrapod-dominated, terrestrial ecosystems formed through the late Palaeozoic. Using morphometric and phylogenetic comparative methods, we chart carnivorous synapsid trophic morphology from the latest Carboniferous to the earliest Triassic (307-251.2 Ma). We find a major morphofunctional shift in synapsid carnivory between the early and middle Permian, via the addition of new feeding modes increasingly specialised for greater biting power or speed that captures the growing antagonism and dynamism of terrestrial tetrapod predator-prey interactions. The further evolution of new hypo- and hypercarnivorous synapsids highlight the nascent intrinsic pressures and complexification of terrestrial ecosystems across the mid-late Permian.
... "Microsaurs" represent a taxonomically problematic group of small-bodied tetrapods that first appeared in the younger (late Moscovian) Florence locality in Nova Scotia (Carroll 1969;Reisz 1971). The rare taphonomy associated with the Joggins tree fauna is also observed at Florence, and involves the remains of temnospondyls (Rieppel 1980;Holmes et al. 1995), embolomeres (Klembara 1985), synapsids (Reisz 1971;Mann and Paterson 2020;Mann and Reisz 2020), a "protorothyridid" eureptile (Carroll 1969), and a "microsaur" (Carroll and Gaskill 1978) preserved within in-situ Sigillaria stumps. ...
... "Microsaurs" represent a taxonomically problematic group of small-bodied tetrapods that first appeared in the younger (late Moscovian) Florence locality in Nova Scotia (Carroll 1969;Reisz 1971). The rare taphonomy associated with the Joggins tree fauna is also observed at Florence, and involves the remains of temnospondyls (Rieppel 1980;Holmes et al. 1995), embolomeres (Klembara 1985), synapsids (Reisz 1971;Mann and Paterson 2020;Mann and Reisz 2020), a "protorothyridid" eureptile (Carroll 1969), and a "microsaur" (Carroll and Gaskill 1978) preserved within in-situ Sigillaria stumps. The only "microsaur" taxon recognized from this site is an unidentified gymnarthrid (Carroll and Gaskill 1978). ...
A new specimen of Batrachichnus salamandroides was recovered from a recently discovered fossil-bearingsite situated along the southern shore of Grand Lake, New Brunswick, among a diverse ichnofaunal assemblagefrom the Middle Pennsylvanian (upper Bolsovian; lower Moscovian), upper Minto Formation. The identity ofthe tracemaker of this ichnogenus is reinterpreted as a composite of various late Paleozoic tetrapod taxa, basedon similarities of the postcranial skeletons, notably that of the manus and pes, of both temnospondyls and some“microsaurs”. These results indicate that the tracemaker of the monospecific ichnogenus Batrachnichus is notlimited solely to a temnospondyl tracemaker, as previously interpreted, and that some “microsaurs” should alsobe considered among tracemaker candidates for this ichnotaxon.
... "Microsaurs" represent a taxonomically problematic group of small-bodied tetrapods that first appeared in the younger (late Moscovian) Florence locality in Nova Scotia (Carroll 1969;Reisz 1971). The rare taphonomy associated with the Joggins tree fauna is also observed at Florence, and involves the remains of temnospondyls (Rieppel 1980;Holmes et al. 1995), embolomeres (Klembara 1985), synapsids (Reisz 1971;Mann and Paterson 2020;Mann and Reisz 2020), a "protorothyridid" eureptile (Carroll 1969), and a "microsaur" (Carroll and Gaskill 1978) preserved within in-situ Sigillaria stumps. ...
... "Microsaurs" represent a taxonomically problematic group of small-bodied tetrapods that first appeared in the younger (late Moscovian) Florence locality in Nova Scotia (Carroll 1969;Reisz 1971). The rare taphonomy associated with the Joggins tree fauna is also observed at Florence, and involves the remains of temnospondyls (Rieppel 1980;Holmes et al. 1995), embolomeres (Klembara 1985), synapsids (Reisz 1971;Mann and Paterson 2020;Mann and Reisz 2020), a "protorothyridid" eureptile (Carroll 1969), and a "microsaur" (Carroll and Gaskill 1978) preserved within in-situ Sigillaria stumps. The only "microsaur" taxon recognized from this site is an unidentified gymnarthrid (Carroll and Gaskill 1978). ...
Un nouveau spécimen de Batrachichnus salamandroides a été récupéré d'un emplacement fossilifère récemment découvert le long de la rive méridionale du Grand Lac, Nouveau-Brunswick, parmi un assemblage ichnofaunique diversifié remontant au Pennsylvanien moyen (Bolsovien supérieur, Moscovien inférieur) de la partie supérieure de la Formation de Minto. On a réinterprété l'identité de l'auteur des traces de cet ichnogenre y voyant un composite de divers taxons tétrapodes du Paléozoïque tardif d'après des similarités des squelettes postcrâniens, notamment ceux des paumes et des pieds, des deux temnospondyles et de certains « microsauriens ». Ces résultats révèlent que l'auteur des traces de l'ichnogène monospécifique Batrachnichus ne se limite pas seulement à un producteur de traces temnospondyle, comme l'avaient supposé des interprétations antérieures, et que certains « microsauriens » devraient également être considérés parmi les producteurs de traces possibles de cet ichnotaxon. [Traduit par la redaction] ABSTRACT A new specimen of Batrachichnus salamandroides was recovered from a recently discovered fossil-bearing site situated along the southern shore of Grand Lake, New Brunswick, among a diverse ichnofaunal assemblage from the Middle Pennsylvanian (upper Bolsovian; lower Moscovian), upper Minto Formation. The identity of the tracemaker of this ichnogenus is reinterpreted as a composite of various late Paleozoic tetrapod taxa, based on similarities of the postcranial skeletons, notably that of the manus and pes, of both temnospondyls and some "microsaurs". These results indicate that the tracemaker of the monospecific ichnogenus Batrachnichus is not limited solely to a temnospondyl tracemaker, as previously interpreted, and that some "microsaurs" should also be considered among tracemaker candidates for this ichnotaxon.
... Temporal openings appeared early in various amniote clades with the oldest known examples postdating the oldest unambiguous amniotes by just a few million years (Reisz, 1972(Reisz, , 1977Modesto & Reisz, 1990;Reisz & Dilkes, 2003;Reisz & Fröbisch, 2014). This implies a rapid emergence and diversification of temporal openings in amniotes compared to other early tetrapods. ...
The diversity and evolution of the temporal skull region is a classical text book example of comparative anatomy. In the earliest land vertebrates this region was, in most cases, completely covered by an armor of dermal bones. This armor has been successively reduced over time, leading most famously to the evolution of temporal fenestrae and marginal excavations. Such temporal openings are widespread in extant Tetrapoda, but especially their great diversity within Amniota (mammals and reptiles, including birds) inspired many early studies on the potential phylogenetic and evolutionary implications of temporal openings. In the early 20th century, this led to various researchers naming new taxa that were mainly defined by their temporal morphology, with Anapsida, Synapsida, Diapsida, and Euryapsida being the most known. Most of these taxa are not considered to represent natural groupings anymore; instead, new fossil findings and analyses confirmed that similar types of temporal openings independently evolved several times within, as well as outside of Amniota. Thus, the main focus of temporal region research has been on their functional morphology. The forces generated by the external jaw adductors hereby seem to play an essential role, but additionally the impact of neck mechanics, skull shape, developmental biology, and others are being discussed. In this short review, we summarize the research history and the current state of art to inspire a more integrative morphofunctional and evolutionary discussion of this widely-known character complex in research and education.
... Amniota has a long evolutionary history extending into the Carboniferous, with the oldest members of this clade having been discovered inside large Sigillaria stumps in Joggins, Nova Scotia (Carroll, 1964;Reisz, 1972). Phylogenetic studies over the course of the past four decades have resolved Amniota as a crown group (see most recent definition in Laurin & Reisz, 2020) and several closely related late Palaeozoic taxa (e.g. ...
... The first appearance of amniotes in the fossil record are represented by fragmentary remains of at least two taxa in the late Carboniferous Sigillaria stumps of Joggins, Nova Scotia [1,2], now dated at 318 Ma [3]. These include the reptile Hylonomus and the synapsid Protoclepsydrops. ...
The initial stages of diapsid evolution, the clade that includes extant reptiles and the majority of extinct reptilian taxa, is surprisingly poorly known. Notwithstanding the hypothesis that varanopids are diapsids rather than synapsids, there are only four araeoscelidians and one neodiapsid present in the late Carboniferous and early Permian. Here we describe the fragmentary remains of a very unusual new amniote from the famous cave deposits near Richards Spur, Oklahoma, that we recognize as a diapsid reptile, readily distinguishable from all other early amniotes by the unique dentition and lower jaw anatomy. The teeth have an unusual reeding pattern on the crown (long parallel ridges with rounded surfaces), with some teeth posteriorly tilted and strongly recurved, while a ventral protuberance forms the anterior terminus of the dentary. Overall, the lower jaw is unusually slender with a flattened ventral surface formed by the dentary and splenial anteriorly and the angular in the mid-region. The presence of a very slender triradiate jugal revealed through computed tomography confirms the existence of a large lower temporal fenestra, while the medial edge of the maxilla and the anatomy of the palatine confirm the presence of a large suborbital fenestra. Computed tomography of this new taxon reveals maxillary innervation that is characteristically reptile, not synapsid. Although no other definitively identifiable skull roof elements exist, the suborbital fenestra borders preserved on the palatine and maxilla supports the hypothesis that this is a diapsid reptile. Interestingly, the right dentary shows evidence of pathology, a rarely reported occurrence in Paleozoic amniotes, with several empty tooth sockets filled by bone. This small predator with delicate subthecodont implanted dentition provides strong evidence that diapsid reptiles were already diversifying rapidly in the early Permian, but likely were relatively rare members of terrestrial vertebrate assemblages.
... In Nova Scotia, Canada, the Florence locality, in strata of the Morien Group of Westphalian D age (Calder 1998), is another tree stump locality. It yielded the edopoid Cochleosaurus, the limnoscelid Limnostygis, an embolomere, the eureptile Palaeothyris and the synapsids Archaeothyris, Echinerpeton and Dendromaia (Carroll 1967(Carroll , 1969Reisz 1972;Klembara 1985;Godfrey and Holmes 1995;Maddin et al. 2020;Mann and Paterson 2020). ...
Tetrapod (amphibian and amniote) fossils of Carboniferous age are known almost exclusively from the southern part of a palaeoequatorial Euramerican province. The stratigraphic distribution of Carbonif-erous tetrapod fossils is used to identify five land-vertebrate faunachrons: (1) Hortonbluffian (Givetian-early Visean), the time between the first appearance datum (FAD) of tetrapods to the beginning of the Doran; (2) Doran (late Visean-early Bashkirian), the time between the FAD of the baphetid Loxomma and the beginning of the Nyranyan; (3) Nyranyan (late Bashkirian-Moscovian), the time between the FAD of the eureptile Hylonomus and the beginning of the Cobrean; (4) Cobrean (Kasimovian-late Gzhelian), the time between the FAD of the eupelycosaur Ianthasaurus and the beginning of the Coyotean; and (5) Coyotean (late Gzhelian-early Permian), the time between the FAD of the eupelycosaur Sphenacodon and the beginning of the Sey-mouran. This biochronology provides insight into some important evolutionary events in Carboniferous tetra-pod evolution.
... Amniotes, the terrestrialized vertebrates, are a diverse group comprising more than 25,000 living species. Their earliest fossils occur around 318 million years ago and already include representatives of the two major subgroups that persist to the present day (Carroll 1964;Reisz 1972): Synapsida (mammal-line amniotes) and Reptilia, or Sauropsida (the stem-lineage of reptiles, including birds; hereafter referred to as Reptilia or "reptiles"). The earliest members of both groups were extremely similar in their general morphology, being small and superficially lizard-like insectivores with sprawling limb orientations. ...
The origin of amniotes 320 million years ago signalled independence from water in vertebrates and was closely followed by divergences within the mammal and reptile stem lineages (Synapsida and Reptilia). Early members of both groups had highly similar morphologies, being superficially 'lizard-like' forms with many plesiomorphies. However, the extent to which they might have exhibited divergent patterns of evolutionary change, with potential to explain the large biological differences between their living members, is unresolved. We use a new, comprehensive phylogenetic dataset to quantify variation in rates and constraints of morphological evolution among Carboniferous-early Permian amniotes. We find evidence for an early burst of evolutionary rates, resulting in the early origins of morphologically distinctive subgroups that mostly persisted through the Cisuralian. Rates declined substantially through time, especially in reptiles. Early reptile evolution was also more constrained compared to early synapsids, exploring a more limited character state space. Postcranial innovation in particular was important in early synapsids, potentially related to their early origins of large body size. In contrast, early reptiles predominantly varied the temporal region, suggesting disparity in skull and jaw kinematics, and foreshadowing the variability of cranial biomechanics seen in reptiles today. Our results demonstrate that synapsids and reptiles underwent an early divergence of macroevolutionary patterns. This laid the foundation for subsequent evolutionary events and may be critical in understanding the substantial differences between mammals and reptiles today. Potential explanations include an early divergence of developmental processes or of ecological factors, warranting cross-disciplinary investigation.
... Thus, there is currently no strong evidence that the sphenacodontid/therapsid divergence is older than Gzhelian. Yet, therapsids are unknown so far in the Carboniferous, with the possible exception of the very fragmentary remains (a string of a few vertebrae) from the Moscovian of Nova Scotia that Spindler (2014) interpreted as a therapsid, an interpretation that seems tenuous at best; the original interpretation that these belong to a sphenacodontid seems plausible (Reisz, 1972). Therapsids may be represented by a single specimen of Tetraceratops in the Kungurian, even though its affinities are still debated (Amson and Laurin, 2011;Spindler, 2020), and beyond the scope of this study. ...
Given a phylogenetic tree that includes only extinct, or a mix of extinct and extant taxa, where at least some fossil data are available, we present a method to compute the distribution of the extinction time of a given set of taxa under the Fossilized-Birth-Death model. Our approach differs from the previous ones in that it takes into account (i) the possibility that the taxa or the clade considered may diversify before going extinct and (ii) the whole phylogenetic tree to estimate extinction times, whilst previous methods do not consider the diversification process and deal with each branch independently. Because of this, our method can estimate extinction times of lineages represented by a single fossil, provided that they belong to a clade that includes other fossil occurrences. We assess and compare our new approach with a standard previous one using simulated data. Results show that our method provides more accurate confidence intervals. This new approach is applied to the study of the extinction time of three Permo-Carboniferous synapsid taxa (Ophiacodontidae, Edaphosauridae, and Sphenacodontidae) that are thought to have disappeared toward the end of the Cisuralian (early Permian), or possibly shortly thereafter. The timing of extinctions of these three taxa and of their component lineages supports the idea that the biological crisis in the late Kungurian/early Roadian consisted of a progressive decline in biodiversity throughout the Kungurian.
The membership, phylogeny and external relationships of Amniota quickly achieved "textbook wisdom" status in the mid-1990s, but were all called into question by phylogenetic analyses in the last few years. However, all these analyses and all their predecessors have either focused on early limbed vertebrates and barely extended into Amniota, or focused on amniotes and included very few non-amniotes as outgroups. Here I take an analysis of the first type, perform corrections and updates, and enlarge its sample of amniotes and amniote-related characters (among other things) in order to test these matters. Despite its very high rates of homoplasy, my matrix supports all "microsaurs" as amphibians, perhaps even less close to Amniota than Seymouriamorpha. For Diadectomorpha its "classical" position on the stem of Pan-Amniota is weakly supported; this stem has, however, greatly expanded to include many supposed amniotes, among others the fish-scaled Brouffia. The recent finding of Petrolacosaurus outside Diapsida, indeed outside Amniota along with Captorhinidae, is—weakly—corroborated despite my quite different taxon and character samples. Caseasauria, normally considered part of Pan-Mammalia, is instead nested among the "parareptiles" within Sauropsida; Varanopidae, similarly traditionally placed among the pan-mammals, instead emerges in three separate sauropsid positions. A period of very small body size around the origin of the amniotic egg is not supported by the optimal trees, but trees that seem compatible with it are nearly optimal. Slightly worse trees allow for aïstopods as limbless anthracosaurs. The generally low support for the trees highlights specific needs for future research. Still, it appears that the recently proposed membership of many traditional "microsaurs" in Amniota can be excluded with reasonable confidence, as can a position of Anthracosauria crownward of Temnospondyli or a temnospondyl origin for any extant amphibians. Coding the temporal bone of "microsaurs" and other taxa as the tabular or the supratemporal has practically no effect.
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