Callibrachion

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Callibrachion
Temporal range: Early Permian, Asselian
Callibrachion18DB.jpg
Life restoration of Callibrachion gaudryi by Dmitry Bogdanov.
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade:† Caseasauria
Family:† Caseidae
Genus:† Callibrachion
Boule and Glangeaud, 1893
Species
  • † Callibrachion gaudryi Boule and Glangeaud, 1893 (type)

Callibrachion is an extinct genus of caseid synapsids that lived in east-central France during the Lower Permian (Asselian). The holotype and only known specimen (MNHN.F.AUT490) is represented by an almost complete postcranial skeleton associated with skull fragments discovered at the end of the 19th century in the Permian Autun basin in Saône-et-Loire department, in the Bourgogne-Franche-Comté region. It belongs to an immature individual measuring less than 1.50 m in length. Callibrachion was long considered a junior synonym of the genus Haptodus and classified among the sphenacodontid pelycosaurs. In 2015, a new study found that Callibrachion was a different animal from Haptodus and that it was a caseasaur rather than a sphenacodontid. This was confirmed in 2016 by a cladistic analysis which recovered Callibrachion as a basal caseid. Callibrachion's sharp teeth and unenlarged ribcage indicate that this animal was likely faunivorous. [1] [2]

Contents

Description

Holotype of the Callibrachion gaudryi preserved on the back (A). Detail of the right hand (B). Right ilium covered dorsally by the proximal end of the femur (C). Coprolites of sharks placed on the slab of the holotype during the 19th century (D). Callibrachion gaudryi 3.jpg
Holotype of the Callibrachion gaudryi preserved on the back (A). Detail of the right hand (B). Right ilium covered dorsally by the proximal end of the femur (C). Coprolites of sharks placed on the slab of the holotype during the 19th century (D).

Callibrachion is known by a relatively complete but poorly preserved skeleton. It is preserved on a black shale slab which exposes the ventral side of the skeleton. The latter consists of a fragmentary skull, the rib cage, the forelimbs, and the right hindlimb. The left hindlimb and tail are missing as well as some parts of the shoulders and pelvis. The exposed notochordal canal and disarticulation of the scapulocoracoid and ilium (where the bony vasculature is visible) indicate an immature ontogenetic stage. In contrast, the well-ossified metapodials indicate that this is not an early juvenile. Although almost complete, no autapomorphies can be identified in Callibrachion due to the generally poor state of preservation of the specimen as well as the great incompleteness of the skull which usually concentrates many distinctive characters. Callibrachion is defined by a combination of characters such as fine and straight conical teeth, moderately thickened ribs, the possible presence of a closed ectepicondylar foramen, an ilium with the high dorsal lamina typical of caseids, robust but not enlarged phalanges, and an unreduced phalangeal formula. [2]

Explanatory drawing of the holotype of Callibrachion gaudryi. Callibrachion gaudryi 4.jpg
Explanatory drawing of the holotype of Callibrachion gaudryi.

The skull is represented by several fragments of which only the maxilla (and possibly a portion of the premaxilla) is an element clearly identifiable by its row of marginal teeth. The ventral margin is slightly convex, with some large caniniform teeth at the anterior end indicated by the broad dental bases unlike the smaller ones preserved posterior to the latter. A second region of enlarged teeth is present posterior to the caniniform positions and is reminiscent of what is observed in eothyridids and in the basal caseid Martensius . It is not possible to provide an exact number of teeth or an estimate of the jaw length because the outline of the bone is uncertain. Preserved teeth have a thin, conical crown with a smooth surface, devoid of any significant curvature except in the anterior part of the preserved tooth row. The mandible is represented by a thin and rather shallow branch of the right jaw. Its preserved length of around 70 mm could be close to its original length, as large and slightly curved teeth are found in what is most likely the end of the dentary. [2]

The vertebral column is represented by about twelve centra of dorsal vertebrae, as well as uncertain remains of the cervical series and neural arches. The tail is not preserved. Two barely visible cervical centra appear to lie between the skull and the shoulder girdle. Some vertebrae have been damaged during preparation, while others are covered by the shoulder girdle. Nevertheless, thanks to the articulation of the skeleton, it is possible to provide an estimate of the presacral number. In particular, the uninterrupted series of approximately 21 dorsal ribs indicates a minimum presacral number of 23 vertebrae. The ribs are robust. In the posterior dorsal region, the ribs decrease in length, but not in width. [2]

The limbs are also strong. A distinctive feature is the scapula much shorter than the humerus. The two manus are fairly well preserved and articulated. The bones of the manus are strong and well developed. However, the metacarpals and phalanges do not exhibit the stocky and enlarged morphology of derived caseids. Their proportions are rather similar to those observed in Eocasea , Martensius , and Casea broilii . The digit IV is the longest in the series. One of its middle phalanges is shortened, measuring about 70% of the length of neighbouring phalanges. Terminal phalanges are strongly curved, with a strong flexor tubercle and an enlarged flat dorsal roof. The manus exhibits the plesiomorphic condition of early amniotes with a phalangeal formula of 2-3-4-5-3. [nb 1] The preserved elements of the right pes are for the most part disarticulated. It is not possible to precise its phalangeal formula, but the individual elements seem to be as robust and strongly developed as those of the manus. [2]

Stratigraphic range

The holotype of Callibrachion was discovered in the 19th century in the Margenne site during oil shale mining then in progress in the Autun basin. The palaeontological richness of this basin allowed at the time to define the Autunian as a reference stage for the continental Lower Permian of Europe. [3] According to modern stratigraphy, the Margenne site belongs to the Millery Formation which is one of the youngest formations of the Autun basin. [4] It corresponds to the upper part of the Autunian of the ancient authors. Based on plant, invertebrate, and amphibian fossils, the Autunian was considered to be an age equivalent to the global marine stages of the late Gzhelian, Asselian, Sakmarian, and Artinskian. [3] [5] [4] Since the end of the 2010s, radiometric dating of volcanic ash (altered in tonsteins) intercalated in the sedimentary layers of several geological formations constituting the Autunian of the Autun basin revealed that the Autunian corresponded almost exclusively to the Asselian of the international geological time scale. [6] [7] The lower Autunian is represented by the Igornay and Muse formations. The middle part of the Igornay Formation is dated at 299.9 ± 0.38 Ma and represents the late Gzhelian (latest Carboniferous), confirming the first age estimates of the oldest Autunian levels. The Lally oil shale bed in the lower part of the Muse Formation is dated at 298.91 ± 0.08 Ma, which corresponds, at ± 100,000 years, to the Carboniferous-Permian boundary set in the marine strata in the Ural Mountains. The upper part of the Muse oil shale bed is dated between 298.05 ± 0.19 and 298.57 ± 0.16 Ma. These dates demonstrate that the lower Autunian corresponds to the late Gzhelian and early Asselian, and therefore encompasses the end of the late Carboniferous and the base of the early Permian. [6] Two other levels of volcanic ash present at the top of the Muse Formation (lower-upper Autunian boundary) and in the upper part of the Millery Formation gave ages of 298.39 ± 0.09 Ma [nb 2] and 297.7 ± 0.08 Ma, the latter indicating an early-middle Asselian age. These dates indicate that the upper Autunian (represented by the Surmoulin, Millery, and Curgy formations) probably did not exceed an Asselian age. [8] [7] Thus, these dates prove that the five geological formations of the Autun basin which defined the Autunian represent a geological duration of less than 2.5 million years and include the Carboniferous-Permian boundary. This duration is significantly shorter than the 10 million years of deposits previously estimated. [7] Thus, the genus Callibrachion from the Millery Formation, whose age was successively considered as Sakmarian or Artinskian, turns out to be older with an early or middle Asselian age. It is thus the oldest known Permian caseid, only surpassed in age by the Carboniferous taxa Eocasea and Datheosaurus .

Paleoecology

The Millery Formation is 250 m thick and consists of dark gray oil shales deposited in a lacustrine environment. [2] [6] The volcanic ash, altered into tonsteins, preserved in these deposits is linked to an aerial explosive volcanism. The exact origin of these volcanic ash is uncertain but the closest active volcanoes to the Autun basin during the Carboniferous-Permian boundary were in the north of the Massif Central (Blismes and Montreuillon areas) and in the Black Forest and Vosges areas. [6] The rare amniotes found in these lacustrine layers, such as Callibrachion, the small sphenacodontid Haptodus and the taxon of uncertain affinity “Belebey” augustodinensis [nb 3] [9] [10] (both known from another site in the same formation) are allochthonous. The temnospondyl Onchiodon , a smaller relative of the genus Eryops from North America, is also present. [11] [12] [13]

Paleobiology

Size comparison of basal caseasaurs including Callibrachion gaudryi. Basal caseasaur size chart.jpg
Size comparison of basal caseasaurs including Callibrachion gaudryi.

The conical, thin, and slightly curved teeth of Callibrachion differ markedly from the spatulate or leaf-shaped teeth with cusps of later herbivorous caseids. They are more like those of the Eothyrididae and the basal caseid Martensius . The former were small predators, the latter was insectivorous in juvenile stage and omnivorous in adulthood. [14] Callibrachion lacked the enlarged rib cage of derived herbivorous caseids which had a voluminous intestine necessary for digestion of high-fiber vegetation. The absence of this characteristic in Callibrachion as well as its particular dentition indicate that it was faunivorous and probably fed on insects and small vertebrates. [2]

Classification

From its description in 1893 until the late 1970s, most paleontologists who studied Callibrachion believed it to be close of species now classified as Sphenacodontidae. Some authors have also considered it to be a junior synonym of the genus Haptodus . In the 1990s, Michel Laurent came to doubt the synapsid nature of Callibrachion (then classified as Haptodus gaudryi) and considered it a nomen dubium . [15] It was not until 2015 that the animal was re-studied by Spindler and colleagues and identified as a caseasaur on the basis of its overall proportions as well as dental and osteological characteristics that exclude it from any other synapsid clades. [2] In 2016, a phylogenetic study of caseasaurs recovered Callibrachion as a basal caseid closely related to Eocasea and Datheosaurus. [16]

Below is the phylogenetic analysis published by Neil Brocklehurst and colleagues in 2016. . [16]

  Caseasauria

  Eothyrididae

  Caseidae

  Eocasea martini

 Callibrachion gaudryi

  Datheosaurus macrourus

  Oromycter dolesorum

  Casea broilii

  Trichasaurus texensis

  Euromycter rutenus

  Casea nicholsi

  Ennatosaurus teton

  Angelosaurus romeri

  Cotylorhynchus romeri

  Cotylorhynchus bransoni

  Cotylorhynchus hancocki

Notes

  1. ↑ The phalangeal formula corresponds to the number of phalanges constituting each digits of the manus and pes of tetrapods. It is listed starting from digit I (corresponding in human to the thumb and big toe) to digit V (the equivalent of the little finger and little toe).
  2. ↑ The inconsistency between this age of 298.39 ± 0.09 Ma from the top of the Muse formation with the younger age of 298.05 ± 0.19 Ma from an older level of the same formation could be explained by a rejuvenated age of the tonstein dated at 298.05 Ma. This rejuvenation would be due to the smaller size of the dated zircon grains and a possible loss of lead (cf. Mercuzot 2020, p. 249-250).
  3. ↑ Assigned to the bolosaurid genus Belebey by Jocelyn Falconnet (2012), this taxon is considered by Spindler and colleagues (2019) to be a nomen dubium, possibly representing an Edaphosauridae or a Captorhinidae .

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<span class="mw-page-title-main">Caseidae</span> Extinct family of synapsids

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<i>Ctenospondylus</i> Extinct genus of synapsids

Ctenospondylus is an extinct genus of sphenacodontid synapsid

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<i>Cotylorhynchus</i> Extinct genus of synapsids

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Angelosaurus is an extinct genus of herbivorous caseid synapsids that lived during the late Lower Permian (Kungurian) and early Middle Permian (Roadian) in what is now Texas and Oklahoma in the United States. Like other herbivorous caseids, it had a small head, large barrel-shaped body, long tail, and massive limbs. Angelosaurus differs from other caseids by the extreme massiveness of its bones, particularly those of the limbs, which show a strong development of ridges, processes, and rugosities for the attachment of muscles and tendons. Relative to its body size, the limbs of Angelosaurus were shorter and wider than those of other caseids. The ungual phalanges looked more like hooves than claws. The few known cranial elements show that the skull was short and more robust than that of the other representatives of the group. Angelosaurus is also distinguished by its bulbous teeth with shorter and wider crowns than those of other caseids. Their morphology and the high rate of wear they exhibit suggests a diet quite different from that of other large herbivorous caseids, and must have been based on particularly tough plants. A study published in 2022 suggests that the genus may be paraphyletic, with Angelosaurus possibly only represented by its type species A. dolani.

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<i>Euromycter</i> Extinct genus of synapsids

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<i>Alierasaurus</i> Extinct genus of synapsids

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<i>Shashajaia</i>

Shashajaia is a genus of extinct non-mammalian synapsids from the late Carboniferous to Early Permian. It was one of the earliest members of the group, coming from the Gzhelian stage. It lived in what is now the Halgaito Formation within the larger Cutler group located in the U.S state of Utah. According to a description study, this synapsid is known from well preserved dentary and jaw fragments. Shashajaia shares many similarities to other sphenacodontids including, enlarged (canine-like) anterior dentary teeth, a dorsoventrally deep symphysis and low-crowned, subthecodont postcanines having festooned plicidentine. The study also found that this genus is close to the evolutionary divergence of the Sphenacodontids and the Therapsids, from which mammalian synapsids arose from. Based on studies done on its teeth, Paleontologists found that as their prey became more terrestrial, synapsids like Shashajaia adapted to life on land and grew larger teeth to deal with larger herbivores in a evolutionary arms race.

<i>Lalieudorhynchus</i> Extinct genus of synapsids

Lalieudorhynchus is an extinct genus of caseid synapsids that lived during the Guadalupian in what is now the south of France. The genus is only known by its type species, Lalieudorhynchus gandi, which was named in 2022 by Ralf Werneburg, Frederik Spindler, Jocelyn Falconnet, Jean-Sébastien Steyer, Monique Vianey-Liaud, and Joerg W. Schneider. Lalieudorhynchus is represented by a partial postcranial skeleton discovered in the Lodève basin in the central part of the Hérault department in the Occitanie region. It belongs to an individual measuring approximately 3.75 m (12.3 ft) in length. The degree of ossification of its bones, however, indicates that it was a late juvenile or still growing young adult. Based on the internal structure of its bones, the describing authors interpreted Lalieudorhynchus as a semiaquatic animal that may have had a lifestyle similar to that of hippopotamus, spending part of its time in water but returning to land for food, though the idea that caseids were semi-aquatic has been previously contested by other authors. It is geologically one of the youngest known representatives of the caseids. The phylogenetic analysis proposed by Werneburg and colleagues identified Lalieudorhynchus as a derived caseid closely related to the North American species "Cotylorhynchus" hancocki.

References

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  2. 1 2 3 4 5 6 7 8 Spindler, F.; Falconnet, J.; Fröbisch, J. (2015). "Callibrachion and Datheosaurus, two historical and previously mistaken basal caseasaurian synapsids from Europe". Acta Palaeontologica Polonica. 61 (3): 597–616. doi: 10.4202/app.00221.2015 .
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  14. ↑ Berman, D.S.; Maddin, H.C.; Henrici, A.C.; Sumida, S.S.; Scott, D.; Reisz, R.R. (2020). "New primitive Caseid (Synapsida, Caseasauria) from the Early Permian of Germany". Annals of Carnegie Museum. 86 (1): 43–75. doi:10.2992/007.086.0103. S2CID   216027787.
  15. ↑ Laurin, M. (1994). "Re-evaluation of Cutleria wilmarthi, an Early Permian synapsid from Colorado". Journal of Vertebrate Paleontology. 14 (1): 134–138. doi:10.1080/02724634.1994.10011544.
  16. 1 2 Broklehurst, N.; Reisz, R.; Fernandez, V.; Fröbisch, J. (2016). "A Re-Description of 'Mycterosaurus' smithae, an Early Permian Eothyridid, and Its Impact on the Phylogeny of Pelycosaurian-Grade Synapsids". PLOS ONE. 11 (6): e0156810. Bibcode:2016PLoSO..1156810B. doi: 10.1371/journal.pone.0156810 . PMC   4917111 . PMID   27333277.
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