Subclass Captorhinomorpha

{ "title": "Captorhinomorphs (Captorhinomorpha) – a group of primitive angustitabulars", "summary": "Captorhinomorphs are a group of reptiles that appeared in the Middle Carboniferous period and reached their peak in the Early and Late Permian periods. They are characterized by their primitive skull structure and are thought to be the ancestors of all eureptiles.", "body": "Captorhinomorphs (Captorhinomorpha) – a group of primitive angustitabulars with an apoparaxial skull construction, inherited from their primitive ancestors, which is expressed in the absence of a wide suborbital bone, scaly. _____ Time of existence and places of known finds _____ It is believed that this group of reptiles appeared in the Middle Carboniferous (Canada), slightly earlier than the pelycosaurs and arioscelids. The first finds (Canada) were not numerous (Middle Carboniferous period). More frequent finds date back to the Late Carboniferous period (North America). The \"dawn\" of this group began to reach, presumably, in the Lower (Western and Eastern Europe) and Upper Permian (China, Eastern Europe, North Africa, Zimbabwe, South Africa). _____ Systematics _____ According to Olson, the captorhinids originated from the eureptiles (Olson, 1947). Mainly, the captorhinomorphs were distinguished as the ancestors of the mammal-like reptiles (Watson, 1957), however, after the development of the concept of parareptiles (Olson, 1947), they were more likely to be referred to as the ancestors of all eureptiles (Carroll, 1991). M.F. Ivakhnenko (2008) presents an interpretation of the formalities that, due to the features of the skull structure, the captorhinomorphs should include all primitive apoparaxial angustitabulars with a stegnal skull, i.e., antracosauromorphs and their derivatives (Diadectomoppha), with the exception of Bolosauridae. In contrast, the Tseajaidae are associated with the Limnoscelidae. Hüne in 1956 attempted to unite the captorhinomorphs with the millerosaurs into one subclass Captorhinidia of primitive eureptiles. Some sources say that this group is the only one that shows some similarity in skull structure with the Lower Carboniferous Westlothiana (Tatarinov, 2006). These sources also indicate that some authors distinguish the primitive captorhinomorphs in the family Protorothyridae (Protorothyridae = Romeriidae). For systematic distinction, it is considered acceptable to use the cranial feature (as in the case of parareptiles). This feature is the degree of reduction of the bones of the temporal row (posttemporal and tabular). Presumably, this is associated with the degree of development of the cervical musculature, which corresponds to a relatively terrestrial lifestyle. If we rely on such authors as Tatarinov, we can say that more than 22 genera of captorhinomorphs have been described. The subclass Captrhrinomorpha includes 2 orders: Order Saptorhinida (1 family, 2 subfamilies, 15 genera) Order Bolosaurida (2 families, 7 genera) The order Saptorhinida Family Captorhinidae (Case, 1911) - Subfamily Saptorhininae (Case, 1911) - Genus Captorhinus (Case, 1895) - Genus Riabininus (Ivanchenko, 1990) - Genus Romeria (Price, 1937) - Genus Labidosaurus (Cope, 1896) - Genus Protocaptorhinus (Clark et Carroll, 1973) - Genus Rhiodenticulatus (Berman et Reisz, 1986) - Genus Acrodonta (Dutuit, 1976) - Genus Saurorictus (Modesto et Smith, 2001) - Subfamily Moradisaurinae (de Ricyles et Taquet, 1982) - Genus Moradisaurus (Taquet, 1969) - Genus Gecatogomphius (Vjuschkov et Tchudinov, 1957) - Genus Kahneria (Olson, 1962) - Genus Rhotianiscus (Olson, 1935) - Genus Lebidosaurikos (Stovall, 1950) - Genus Captorhinikos (Olson, 1954) - Genus Moradisaurus (Taquet, 1969) The order Bolosaurida Family Bolosauridae (Cope, 1878) - Genus Bolosaurus (Case, 1878) - Genus Stepnospohdylus (Stappenbeck, 1905) - Genus Timanosaurus (Gubin, 1993) - Genus Gnirhimosuchus (Efremov, 1951) Family Belebyidae (Ivachenko, 2001) - Genus Beley (Ivachnenko, 1973) - Genus Davletkulia (Ivachnenko, 1990) - Genus Permotriturus (Tatarinov, 1968) _____ Morphology _____ Having in mind the systematic composition, we can provide some aspects of the morphological features of the representatives of this subclass. As a rule, the representatives of this taxon are divided into small omnivorous/insectivorous with conical teeth (order Captorhinida) and larger herbivorous with a developed secondary palate and possessing a subapsid window (order Bolosaurida). Their representatives had a stegnal skull roof (without temporal openings) or only with one subapsid window. The tabular and posttemporal bones (bones of the temporal row) are significantly reduced; they do not extend to the dorsal surface of the skull roof and can be preserved only in the form of occipital plates. In other words, the tabular and paired posttemporal bones are shifted to the occiput, the occipital posterior temporal window is absent. The postquadratic auditory incision is absent. The scaly bone is narrow and developed only along the posterior-lateral corner of the parietal bone, and the scaly bone is relatively wide and separates the supratemporal bone from the postfrontal. The paroccipital process of the otoccipital bone is rudimentary and does not reach either the scaly or tabular bone. The palate has a movable basipterygoid joint, a small interpterygoid fossa, and well-developed transverse processes of the pterygoids with pronounced transverse flanges. The representatives of the order Captorhinida are characterized by a relatively massive, narrowed skull in which the temporal openings and the secondary palate (palatine flanges) in the jaws are absent. The teeth can be conical, bluntly cylindrical, multi-rooted. The representatives of the family Protorothyridae, which have a controversial systematic position, are known as small lizards with a skull 4-5 cm long, and the body with a tail and relatively short limbs reaches 35-50 cm. They presumably fed on insects or small animal food. The skull, based on general features, is similar to that of the solenodons, but without an auditory incision. On the parasphenoid and pterygoids with processes, there are rows of palatal teeth, sometimes extending to the palatine bones, but without shagreen fields of small teeth on the palate. The auditory ossicle is of the \"theropod\" type, at the ends lies in the direction of the quadratum, above the area of the medial condyle of the jaw joint. In the vertebral column, there are up to 32 precocial vertebrae, the atlas and epistropheus are of the proreptilian type with an independent intercentrum of the latter. The neural arches of the vertebrae are not simplified (unlike the seymouriamorphs, diadectomorphs). The interclavicle is T-shaped. The pelvic girdle is plate-like, the articulating process is directed backward, the upper process of the antracosauromorph type is absent (Holmes, 1977). The foot, as a rule, has a not fully fused reptilian astragalus. The abdominal ribs are transverse rows of elongated scales. In contrast to the protorothyrids, the typical Permian captorhinids are slightly larger. Their possible mollusk-eating is indicated by the multi-rowed blunt jaw teeth. The paroccipital process in the captorhinids is lengthened and connected with the scaly bone. Thus, we can say that they reach the seymouriamorph level. The typical captorhinids lose the tabular bones and ectopterygoids, as well as the teeth on the parasphenoid. The neural arches on the vertebrae are expanded (unlike the protorothyrids). There are two sacral vertebrae. A distinctive feature is the isolated scapula of the shoulder girdle with two coracoids. Some authors suggest the formation of a complex astragalus in the captorhinids due to the fusion of the tibiale, intermedium, and proximal centrale (however, in Labidosaurus, the intermedium does not fuse with the tibiale). In the family Captorhinidae, the skull is elongated in the preorbital part. The representatives of this family can be represented by the following forms: - small, with single-rowed jaws (in some cases up to 3 rows (Tatarinov, 2008)) - subfamily Captorhininae - large, with 5-10 rows of teeth in the jaws - subfamily Moradisaurinae -[IMG_1] Figure 1: Dental bones of representatives of the family Captorhinidae -[IMG_2] Figure 2: Representatives of the family Captorhinidae (reached 40-80 cm in length) _____ Bright representatives of the family Captorhinidae _____ - Subfamily Captorhininae (Case, 1911) Captorhinus aguti Cope, 1882 -[IMG_3] -[IMG_4] Naosaurus uralensis Riabinin, 1915 -[IMG_5] Have a massive, slightly protruding forward and downward, premaxillary bone, which bears no more than three teeth. On the dental bone - no more than 15 teeth in one row. The two front teeth are enlarged, with slightly flattened longitudinal crowns, the rest gradually decrease in size caudally, without changing shape. Riabininus uralensis Riabinin, 1915 -[IMG_6] The length of the skull is no more than 5 cm. The jaw teeth are massive, pointed. Early Permian of Eastern Europe. Type locality: coeval locality of Inta, Inta district, Russia. - Subfamily Moradisaurinae (de Ricyles et Taquet, 1982) Gecatogomphius kavejevi Vjushkov et Tchudinov, 1957 -[IMG_7] Middle Permian of Eastern Europe. In the upper jaw, 6 parallel, non-converging tooth rows, in the lower jaw - 5 anterior conical teeth, increasing in size, with slightly simplified longitudinal crowns, with weakly expressed lateral canters and 5 non-converging rows of bluntly cylindrical teeth, no less than 11 teeth in a row. Moradisaurus Taquet, 1969 -[IMG_8] Early Permian of North America. Large, with 5-10 rows of teeth in the jaws. The representatives of the order Bolosaurida had a short and high skull with a lower temporal window at the junction of the squamosal, scaly, and jugal bones. An incomplete bony palate may be formed due to the wide phalanges of the palatal bones. The teeth have pronounced pterygoid processes. In the family Bolosauridae (Cope, 1878), the maxillary bone is quite short (no more than one-third of the skull length). The crowns of the teeth are high, club-shaped. The uncomplicated pterygoid processes are well-expressed, located obliquely subvertically or almost subhorizontally, at the base rounded or weakly oval. From one to three last jaw teeth are conical, as the size decreases towards the base. Some authors (Ivanchenko, 2008) believe that a weakly expressed secondary palate could have been present. In contrast to the representatives of the previous family, in the family Belebyidae (Ivachenko, 2001), the maxillary bone is long (more than half of the skull length). The crowns of the teeth are low, flattened, with well-expressed wide horizontal pterygoid processes, which are compressed transversely at the base. In contrast to the representatives of the previous family, in this case, the size increases caudally, so that the last teeth are massive, with well-expressed horizontal pterygoid processes. The secondary palate is well-expressed, as the palatine bone almost halves the posterior part of the bony choana. -[IMG_9] _____ Bright representatives of the family Bolosauridae _____ Family Bolosauridae (Cope, 1878) Bolosaurus striatus Cope, 1878 -[IMG_10] Early Permian of North America. Stephanospondylus traati Tatarinov, 1974 -[IMG_11] The length of the skull is no less than 7-8 cm. At the base of the teeth, there are noticeable traces of folding. The tooth row contained 13-14 teeth, the height of the crown of which is slightly less than the height of the neck (the ratio of the diameter of the crown of the middle tooth of the maxilla to the height is 1:3) Timanosaurus ivachnenkoi Gubin, 1993 Middle Permian of Eastern Europe. Described from separate vertebrae, similar to those of bolosaurs, to a lesser extent diadectids and parareptiles. If we look at the formalities, then from the vertebrae of diadectids, they differ in the absence of additional articulations, from parareptiles - by higher neural arches. Family Belebyidae (Ivachenko, 2001) Belebey vegrandis Ivachnenko, 1973 -[IMG_12] The length of the skull is more than 6 cm. The premaxillary bone is massive, the crowns of the buccal teeth are slightly protruding laterally. The two anterior buccal teeth are small, in shape identical to the subsequent teeth. In the maxillary bone, the anterior tooth is incisiform, in shape repeating the incisors of the premaxillary bone, after which a small diastema follows. The finds were discovered on the territory of Russia (Orenburg region, Alexandrovsky district) (skeleton without a skull) and Northern China (Gansu province) (jaw bone). Belebey maximi Tverdochlebova, 1987 -[IMG_13] A small form with a skull length of no more than 4 cm. The dental bone is very thin, the crowns of the buccal teeth are strongly expanded and significantly protruding laterally. The location of the finds is the territory of Russia. Davletkulia gigantea Ivachnenko, 1990 -[IMG_14] The length of the skull is no more than 15-16 cm. The crowns of the buccal teeth are oval, strongly expanded transversely, the surface of the crown is flattened, almost without an expressed cutting edge (tooth apparatus of the grinding type). The finds belong to the Middle Permian of Eastern Europe. Permotriturus herrei Tatarinov, 1968 -[IMG_15] The finds belong to the Middle Permian of Eastern Europe. The length of the skull is approximately 7 cm. They have a very massive dental bone. It is believed that the crowns of the buccal teeth are very flattened transversely (judging by the preserved bases). Since the upper edge of the dental bone is massive and strongly expanded, it is assumed that there were crushing-grinding teeth (like those of Davletkulia) but with strongly compressed bases. _____ List of used literature _____ M.F. Ivakhnenko, E.N. Kurochkin (eds.). Fossil vertebrates of Russia and adjacent countries. Fossil reptiles and birds. Part 1. Handbook for paleontologists, biologists, and geologists. - M.: GEOS, 2008. - 348 p. L.P. Tatarinov. Essays on the evolution of reptiles. Archosaurs and mammal-like reptiles. - M.: GEOS, 2009. - 377 p. https://paleodb.org/cgi-bin/bridge.pl?a=home https://phys.org/news/2011-05-captorhinid-reptile-china.html https://dinosaurs.wikia.com/wiki/Bolosauridae https://www.reptileevolution.com" }