Richards Spur Research Articles

Microleter mckinzieorum gen. et sp. nov. from the Lower Permian of Oklahoma: the basalmost parareptile from Laurasia

The Lower Permian fissure fill deposits near Richards Spur (a.k.a. the Fort Sill locality), Oklahoma, have produced a remarkably rich, diverse, and well-preserved assemblage of fully terrestrial tetrapods, including the parareptiles Bolosaurus grandis, Colobomycter pholeter and Delorhynchus priscus. This study describes a superbly preserved new parareptile, Microleter mckinzieorum gen. et sp. nov., recently recovered from the site. The fossil consists of a small, gracile, mostly articulated skull with an attached lower jaw. Distinct sculpturing is present consisting of small pinprick-size pits interspersed among larger round pits, with shallow grooves radiating to the edges of some of the bones, a pattern somewhat similar to both the Oklahoman parareptile Acleistorhinus and the millerettids from South Africa. Microleter also possesses a temporal fenestra, bounded by the jugal, quadratojugal, postorbital and squamosal but open ventrally. In addition to possessing a very broad palatine, there is an indication that the lacrimal reached the naris, a feature shared with more basal parareptiles. A phylogenetic analysis, using both parsimony and Bayesian algorithms, of Palaeozoic parareptiles indicates that Microleter falls fairly basally, between the millerettids and the group including Acleistorhinus and lanthanosuchids. As such this taxon fills a significant gap in our knowledge of Early Permian and basal parareptiles, with interesting implications for biogeography. Whereas previous evidence argued for an initial Gondwanan diversification of parareptiles, the early age and basal phylogenetic position of this taxon and other parareptiles from Laurasia make this hypothesis problematic.

A RE‐EVALUATION OF SPHENACODONTID SYNAPSID MATERIAL FROM THE LOWER PERMIAN FISSURE FILLS NEAR RICHARDS SPUR, OKLAHOMA

Abstract: Early Permian terrestrial vertebrate faunal assemblages of Laurasia are dominated by large ophiacodontid, sphenacodontid, and edaphosaurid synapsids. This pattern contrasts with the fauna recovered from the Early Permian fissure fill deposits near Richards Spur, Oklahoma, where derived nontherapsid synapsids are rare. The fragmentary remains of Thrausmosaurus serratidens constitute the only published report of Sphenacodontidae from this locality. Here, we re‐evaluate T. serratidens in light of new information on the faunal assemblage of this locality. We confirm that the type material of T. serratidens cannot be assigned to Sphenacodontidae and conclude that it pertains to an indeterminate varanopid. We also describe new material, including a partial maxilla, several isolated jaw fragments with teeth, an isolated precaniniform tooth and a posterior cervical vertebra that represents unequivocal sphenacodontid remains from the Richards Spur assemblage. This material is the first definitive record of a eupelycosaurian synapsid other than a varanopid from this important locality. Faunal similarities between Richards Spur and the Bromacker Quarry, Germany, may be reflective of upland terrestrial communities during the Early Permian.

A new Lower Permian amphibamid (Dissorophoidea, Temnospondyli) from the fissure fill deposits near Richards Spur, Oklahoma

ABSTRACT The fissure fills of Richards Spur, Oklahoma, together constitute the most productive Paleozoic continental fossil locality in the world, having produced a wealth of terrestrial vertebrates, including occasional articulated skeletons. A new dissorophoid amphibian is represented by two skulls: an exquisitely preserved, complete small skull and the posterior part of a second skull, almost twice the size of the holotype. The specimens provide detailed information about the skull roof, palate, braincase, and mandible, showing that this new taxon is characterized by a relatively elongate skull with large tabulars and postparietals, and monocuspid, recurved teeth that show no sign of pedicelly. The large, laterally expanded interpterygoid vacuities are covered by a mosaic of small dermal plates, each carrying more than a dozen strongly recurved teeth. A phylogenetic analysis of 17 ingroup taxa and 62 cranial and postcranial characters yielded a single most-parsimonious tree with the new taxon in a monophyletic Amphibamidae as the sister taxon to the Lower Triassic Micropholis from South Africa. In addition, the new analysis supports a basal split of Amphibamidae into two distinct clades, one containing the new taxon, Micropholis, along with Tersomius, and the other comprising Amphibamus, Gerobatrachus, Doleserpeton, Platyrhinops, Plemmyradytes, Eoscopus, and Georgenthalia. The data retrieved from this new taxon provides insights into the evolution and diversity of the Amphibamidae.

Cranial anatomy of Ennatosaurus tecton (Synapsida: Caseidae) from the Middle Permian of Russia and the evolutionary relationships of Caseidae

ABSTRACT Detailed description of the Middle Permian Russian caseid Ennatosaurus tecton shows that three autapomorphies distinguish it from other caseids: a broad anterior ramus of the jugal, a large contribution of the frontal to the dorsal orbital margin, and a relatively narrow parasphenoid body. Phylogenetic analysis of Caseidae yields a single most parsimonious tree and its topology posits Ennatosaurus tecton as the sister taxon to the clade of the North American caseids Angelosaurus dolani and Cotylorhynchus romeri. Phylogenetic analysis supports the position of Oromycter dolesorum from the Lower Permian Richards Spur locality as the most basal member of Caseidae. In addition, the genus Casea is resolved as paraphyletic, whereby C. rutena forms the sister taxon to the clade containing E. tecton, C. romeri, and A. dolani. The current topology reveals that the pattern of dental complexity in terms of the number of apical cuspules is homoplasious, cautioning against its use as a unidirectional phylogenetic character.

An Early Permian varanodontine varanopid (Synapsida: Eupelycosauria) from the Richards Spur locality, Oklahoma

ABSTRACT Description of the first varanodontine varanopid material from the highly fossiliferous limestone fissure fill deposits at Richards Spur (Dolese Brothers Limestone Quarry), Oklahoma, is based on elements of at least three individuals recovered from two separate blocks of sedimentary rock. One block, which yielded associated cranial and postcranial bones from both adult and juvenile individuals, includes two well-preserved parabasisphenoid complexes, vertebrae, forelimb, pelvic girdle, and hind limb bones. An isolated maxilla fragment from another block preserves the diagnostic dorsal process characteristic of varanodontines. Preserved cranial and postcranial material is virtually identical to the varanodontine Varanops brevirostris. Taxonomic assessment of this new material in the context of the most comprehensive phylogenetic analysis of Varanopidae to date indicates the Richards Spur varanodontine is referable to Varanops brevirostris based on distinctive characters of the maxilla and the parabasisphenoid. The large size of Varanops suggests it was one of the top predators of the Richards Spur ecosystem. The Richards Spur locality records the only known co-occurrence of a mycterosaurine and a varanodontine varanopid at a single locality, and varanopids are the most common synapsids in the assemblage. As generally rare components of the more typically preserved lowland environments, the relative abundance and diversity of varanopids at Richards Spur suggests that they may have been more common components of the upland ecosystems in the Early Permian.

Oromycter, a new caseid from the Lower Permian of Oklahoma

ABSTRACT Superbly preserved skeletal elements of the new taxon Oromycter dolesorum from the Lower Permian deposits in the Dolese Quarry, near Richards Spur, Oklahoma, record the earliest known evidence of a member of Caseidae. Although found as isolated elements, there is strong circumstantial evidence that the maxillae, premaxillae, lacrimal, and dentary belonged to a single individual. Isolated axial and appendicular elements from this locality are also tentatively attributed to this new form. Caseasaur autapomorphies of Oromycter include the presence of the premaxillary rostral process, indirect evidence for an external shelf on the nasal, and lateroventrally tilted external maxillary surface. Caseid autapomorphies include the anterodorsally oriented maxillary process, the short, tall lacrimal, typical caseid ornamentation on the lacrimal, procumbent anterior dentition, largest teeth located anteriorly on each bone, and spatulate, lingually curved marginal dentition. However, the available evidence indicates that Oromycter is a sister taxon to all other caseids because it lacks the leafy serrations on the teeth, has a relatively long lacrimal bone, has a larger number of marginal teeth than most other caseids, lacks an external narial shelf on the maxilla while one is poorly developed on the lacrimal. The presence of this early, basal member of the Caseidae at the Dolese Quarry is consistent with the hypothesis that the initial evolutionary history of this group of herbivores occurred away from the typical deltaic, floodplain depositional environments that preserve the majority of the known Permo-Carboniferous terrestrial vertebrate communities.

A NEW DIADECTID (DIADECTOMORPHA), OROBATES PABSTI, FROM THE EARLY PERMIAN OF CENTRAL GERMANY

A new genus and species of the herbivorous Diadectidae, Orobates pabsti, is described on the basis of several specimens, including two complete, articulated skeletons, a skull with partial postcranium, a partial skull, and a dentigerous jaw fragment. All were collected from the Lower Permian (Wolfcampian) Tambach Formation, lowermost formational unit of the Upper Rotliegend of the Bromacker quarry locality in the midregion of the Thuringian Forest near Gotha, central Germany. A combination of autapomorphic and plesiomorphic character states clearly distinguishes O. pabsti from all other well-known members of Diadectidae and identifies it as the sister taxon to all other diadectids.The description of Orobates pabsti expands further our understanding of the Late Pennsylvanian-Early Permian Diadectidae and records the earliest specialization of tetrapods to high-fiber herbivory.On the basis of paleobiological and paleoenvironmental data only one other Early Permian locality is comparable to the Bro-macker locality, the somewhat younger (Leonardian) fissure fill deposits at Richards Spur, southeastern Oklahoma. This further supports the previously proposed hypothesis, based on similar grounds, that the vertebrates of both localities may have been part of a widespread, terrestrial upland faunal assemblage during the Early Permian.

The hind limb ofCaptorhinus agutiand the step cycle of basal amniotes

Exquisitely preserved limb elements of Captorhinus aguti from the Lower Permian locality of Richards Spur, Oklahoma, form an excellent basis for analysing the step cycle of the hind limb of basal amniotes. An articulated composite hind limb skeleton is moved through the step cycle. These movements are constrained by the intrinsic skeletal anatomy and data from fossilized footprints attributed to Palaeozoic amniotes. Two well-defined hinge joints are evident: a distal tarsometatarsal joint, and a mesotarsal joint between the calcaneum–astragalus–centrale unit and distal tarsals. A strict homology between the latter and mesotarsal joint in lepidosaurs is uncertain. The conspicuous size disparity between the distal end of the tibia and the much larger tibial facet of the astragalus, a widespread feature of archaic amniotes, permits considerable movement between the distal end of the tibia and astragalus during the stance phase. Differential dorsoflexion, concentrated at the preaxial side of the mesotarsal joint, allows the pes to remain stationary (rather than slide laterally) on the substrate as the femur is retracted and the tarsus shifts from an anterior to lateral orientation. The distal end of the femur describes an arc of only ~60° during the stance phase, but could rotate about 60° about its long axis, a figure comparable to that recorded for living lizards.

A new microsaur (Tetrapoda: Lepospondyli) from the Lower Permian of Richards Spur (Fort Sill), Oklahoma

Bolterpeton carrolli n.gen. n.sp. is described from the Lower Permian fissure-fill deposits of Richards Spur, Oklahoma. Bolterpeton is united with the gymnarthrid microsaur Cardiocephalus by having teeth compressed labiolingually, a narrow anterior process of the prearticular penetrating the splenial, and the arrangement of the contacts among the splenial, prearticular, and coronoids. It is united with both Cardiocephalus and Euryodus by the size and distribution of the coronoid teeth and the presence of longitudinal striations of enamel on the lingual tooth surface. Unlike those two genera Bolterpeton has peg-like teeth, but it remains unknown whether this represents the primitive condition or a reversal of the massive conical teeth typical of gymnarthrids. Bolterpeton possesses a flat lamina that runs along the lingual surface of the tooth margin. Where two laminae meet at the point of the tooth a labiolingual ridge is formed, which is most pronounced at smaller sizes. Reexamination of Cardiocephalus shows it to have the same morphology on its "incisors." Previous authors have defined teeth bearing this ridge as "weakly bicuspid." If this ridge were homologous with the "strongly bicuspid" condition of lissamphibians, Bolterpeton would provide the first example of this tooth morphology in lepospondyls and would strengthen recent hypotheses suggesting lepospondyls gave rise to some, if not all, modern amphibians.

Captorhinus magnus, a new captorhinid (Amniota: Eureptilia) from the Lower Permian of Oklahoma, with new evidence on the homology of the astragalus

The new species of single tooth-rowed captorhinid reptile Captorhinus magnus n. sp. from the Lower Permian fissure fillings at Richards Spur, Oklahoma differs from Captorhinus aguti in body size and dental and femoral morphology. Linear measurements of fully mature C. magnus elements range in size from 1.5 to 2.3 times as great as those of C. aguti, and the proximal articular surface of the femur, which is convex in C. aguti, is concave throughout ontogeny. C. magnus possesses ogival cheek teeth aligned in a single row, indicating that ogival dentition can no longer be considered unique to C. aguti. A phylogenetic analysis of captorhinid interrelationships indicates that C. aguti and C. magnus form a clade that possesses a sister-group relationship with Captorhinus laticeps. Incompletely ossified astragali referred to C. magnus provide unequivocal evidence that the astragalus of Captorhinus formed through the fusion of three, originally separate ossifications, the tibiale, intermedium, and proximal centrale, rather than from a single ossification center. At the Richards Spur locality, C. magnus is the most abundant Captorhinus species produced from the deeper, stratigraphically lower sediments of the quarry. It is rare, however, in the uppermost, presumably younger deposits, where C. aguti represents the most numerous Richards Spur captorhinid.

A new early Permian bolosaurid reptile from the Richards Spur Dolese Brothers Quarry, near Fort Sill, Oklahoma

ABSTRACT Dentary and maxillary fragments represent the first documented evidence of a bolosaurid reptile, Bolosaurus grandis, sp. nov., from the Lower Permian (Leonardian) fissure fills of the Dolese Quarry, near Richards Spur, Oklahoma. The discovery of bolosaurid remains at this unique site, characterized by the preservation of exclusively terrestrial tetrapods, is of particular interest because they bridge the temporal gap in the evolutionary history of bolosaurids between the Wolfcampian Bolosaurus striatus of Texas and the much younger, Upper Permian (Kazanian) Belebey of southern Russia. They also provide new information about the mandibular and dental anatomy of this enigmatic group of early amniotes.

A diadectid (Tetrapoda: Diadectomorpha) from the Lower Permian fissure fills of the Dolese quarry, near Richards Spur, Oklahoma

A diadectid (Tetrapoda: Diadectomorpha) from the Lower Permian fissure fills of the Dolese quarry, near Richards Spur, Oklahoma

Large dissorophoid skeletal elements from the Lower Permian Richards Spur Fissures, Oklahoma, and their paleoecological implications

ABSTRACT Skeletal remains attributable to large dissorophoid amphibians, including four femora, two humeri, and an isolated palatine bone, have recently been recovered from the Lower Permian fissure fill deposits at Richards Spur, Oklahoma. Three of the femora are assignable to Acheloma cumminsi. One humérus represents an indeterminate trematopid, perhaps A. cumminsi, whereas the remaining humerus and femur are evidently of dissorophid origin and probably assignable to Cacops. The palatine bone is of unusual morphology and evidently represents a third distinct large dissorophoid taxon. Although the Richards Spur faunal assemblage is unquestionably dominated by small animals such as Captorhinus aguti, Cardiocephalus, and Euryodus, the discovery of rare, larger skeletal elements at the site implies that some elements of the fauna approached or slightly exceeded a body length of about one meter. Although probably uncommon in the vicinity of the fissures, such larger species were clearly not excluded from the deposits by preservational biases. Like other taxa known from Richards Spur, the dissorophoids were fully terrestrial as adults, and their presence reinforces previous interpretations of the Richards Spur paleoenvironment as an arid highland region. However, some Richards Spur taxa have also been reported from lowland “deltaic” localities such as South Grandfield, Oklahoma, implying that their distribution was more cosmopolitan.

Colobomycter pholeter from the Lower Permian of Oklahoma: a parareptile, not a protorothyridid

ABSTRACT Reexamination of the holotype of Colobomycter pholeter and description of a new specimen, from a Lower Permian fissure fill near Richards Spur, Oklahoma, reveals that this small enigmatic reptile is not the youngest known protorothyridid, but instead is one of the earliest parareptiles. Parareptilian apomorphies that are present include an anterior lateral maxillary foramen, a transversely broad antorbital buttress formed by the prefrontal and lacrimai, and a single median posterior emargination of the skull roof. The last feature is recognized for the first time as a parareptilian synapomorphy. The anterior lateral maxillary foramen of parareptiles is confirmed to be the lateral egress of a canal that opens into the nasal chamber. Colobomycter is the sister taxon of the parareptile Acleistorhinus pteroticus, known from the Lower Permian South Grandfield locality of Oklahoma. Together these two taxa comprise Acleistorhinidae, the oldest known parareptilian clade. The group is diagnosed by two synapomorphies: (1) the largest tooth is positioned far anteriorly on the maxilla; and (2) cranial ornamentation comprises sparse, shallow circular dimples.

First record of Seymouria (Vertebrata: Seymouriamorpha) from Early Permian fissure fills at Richards Spur, Oklahoma

Isolated skeletal elements of the amphibian genus Seymouria were recently discovered at the Richards Spur locality near Fort Sill, Oklahoma, a prolific source of Early Permian tetrapod remains. Five of the seven described bones are of juvenile size and include three neural arches, a humerus, and a femur, whereas the other two are partial vertebrae, apparently adult. All seven are morphologically similar to equivalent skeletal elements in Seymouria specimens previously collected in Europe and North America, apart from features reflecting the early developmental stage of the juvenile bones. The femur and humerus are clearly distinct from those of other seymouriamorphs such as Ariekanerpeton and Kotlassia. The rarity of Seymouria at the Richards Spur locality implies that it was not a regular component of the fauna, and it is also associated with the less markedly terrestrial assemblage that consistently occurs at localities in the southwestern United States. However, its skeletal morphology and occurrence at terrestrial localities such as Richards Spur imply a primarily terrestrial, rather than an amphibious, mode of life. Conflicting biostratigraphic correlations imply that the exact age of the Richards Spur deposits is uncertain, and equivalence to the Arroyo Formation of Texas may be erroneous.

Hot springs along the Alpine Fault, Cascade River Valley, South Westland, New Zealand

Abstract Hot springs are reported from the base of Richards Spur, Cascade River Valley, South Westland, New Zealand. The springs are located at the western boundary of Dun Mountain Ophiolite Belt in the area and are thought to be associated with the Alpine Fault.