Labidosaurikos is a genus of extinct captorhinid tetrapods that lived around 279 to 272 million years ago during Kungurian age of the lower Permian. The American paleontologist John Willis Stovall first described Labidosaurikos in 1950, naming it "Labidosaurus like" for the striking similarity of the holotype skull of his specimen to the cranial anatomy of another captorhinid Labidosaurus hamatus. Labidosaurikos is an important find in Permian red beds of North America, where captorhinids are commonly found, as it is a key discovery in the evolution of herbivory in large captorhinids given its multi-row tooth plates. This is a characteristic it does not share with its name-sake Labidosaurus hamatus whose dentition resembles more basal, mainly single-tooth-rowed forms. The first fossils of Labidosaurikos came from Oklahoma and later finds were discovered in Texas. Most information attributed to Labidosaurikos is based on the cranial anatomy of the only well supported species Labidosaurikos meachami as there are no collections of the appendicular skeleton. Captorhinid anatomy and interrelationships are known primarily from other lower Permian genera such as Romeria, Protocaptorhinus, Rhiodenticulatus, Captorhinus and Labidosaurus. Labidosaurikos is a part of a less well known collection of captorhinids from younger Permian deposits, Moradisaurus is an example.
Description
Labidosaurikos was a large herbivorous tetrapod. Its skull was anapsid (lacking temporal fenestrae) and heavily ornamented, with a hooked snout characteristic of all captorhinids. The consensus on representative species of the genus Labidosaurikos is Labidosaurikos meachami as this is the proposed species type with the most complete fossil skull and jaw. Estimations of body length come in at about 1.3 meters based on ratios of body length to skull length in other large herbivorous captorhinids like Captorhinus aguti. However most anatomical descriptions are limited by the fact that only skulls and cranial and mandible fragments make up the fossil record. Without appendicular skeleton or fragments there cannot be evidence-based description of more morphology aside from the skull.
Skull Of the Labidosaurikos fossil collection the largest adult skull specimen was 280 mm (11 in) making it the second largest captorhinid compared to Moradisaurus gandis, a fellow member of the multiple rowed tooth plate captorhinid subfamily Moradisaurinae. Labidosaurikos skull has broadly flared posterior cheeks that are seen in all other multitoothed taxa as well as its Labidosaurus name sake. The foramens present on the skull include a pineal foramen on dorsal plane and the orbits and external naires that are elliptical in appearance. On the skull roof the frontal bones are little more than a third of the total length of the skull and have parallel sided that terminate posteriorly on a connection perpendicular to the antero-posterior axis. In addition Labidosaurikos characteristically long and slender Prefrontals with lacrimals that are wide and narrow moving anteriorly towards the nares are key characters for which the initial resemblance to Labidosaurus was noted. A captorhinid feature, the long hooked snout consists of a long overlapping junction between nasal and lacrimal bones although the nasal is slightly broader than those of most other captorhinids and extends ventrolaterally slightly more than half-way down the snout. More posterior features includes post frontals and post orbitals that are comparatively short and differ only slightly in size. The parietals are described as arched and the pair of parietals give the skull roof a slightly domed appearance unlike the parietals of other captorhinids. Each one of the parietals is bowed parasaggitally and overlaps sutures of several skull roof elements. When examining these overlapping skull roof elements and the dorsal portion of the skull as a whole there is significant dermal sculpturing. Large pits surround the post parietal suture and are deeper than all other pits that occur on the skull.
Palate and dentition The palate of Labidosaurikos shares a general resemblance to the captorhinid pattern however; there are some specializations that come with the presence of multiple rows of teeth. Some of these features include transverse constriction of the palate by medially expanding tooth laminae of the maxillae and the loss of teeth from the palatine and anterior process of the pterygoid. The vomer is exceptionally slender, long and smoothly convex anteriorly which is a trait shared by Moradisaurus. The anteroventrally directed premaxillae which contain five long premaxillary teeth that decrease in size posteriorly as is the case in other captorhinids. The maxilla is greatly enlarged medially this constricts the palate and forms a tooth plate that accommodates the 6 parallel rows of teeth. Teeth that occur in the maxilla have been considered isodonts. The lateral surface of the maxilla presents a lateral flexion that is a characteristic cheek swelling seen in the single rowed Labidosaurus, Captorhinus aguti and other multi rowed genus. In addition the septomaxilla is characteristic of the family group, however it sports a sculptured postero-dorsal process extending onto the skull roof to insert between lacrimal and nasal. Much like expansion in the maxillae the dentaries expand transversely on the alveolar accommodate multiple rows of teeth. These 6 rows conical peg like teeth occur on medially expanded on both maxillae and dentaries.
Paeloenviornmental information and paleobiology
Environment Labidosaurikos specimens have been found in Permian red beds of North American. Specimens have been found within Hennessey shale in Crescent, Oklahoma as well as the Lower Vale, Choza, and Arroyo Formations in northern central Texas. These locations have yielded critical information about early tetrapod evolution and Captorhinids are extremely common in these deposits. All locations have been correlated with each other to be formed in the Lower Permian sometime within the Kungurian. The colored beds with alternating distinctive red-green margins are formed by nonmarine and marine series of sediments that were deposited contemporaneously over time. The alternative sedimentation indicates the environment Labidosaurikos inhabited were the margins of the aquatic reservoirs that were plentiful in these areas during early Permian time and were able support substantial flora.
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