Ascendonanus
| Ascendonanus | ||||||||||||
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Reconstruction of the skull of A. nestleri |
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| Temporal occurrence | ||||||||||||
| Sacmarium / Artinskium | ||||||||||||
| 290 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Ascendonanus | ||||||||||||
| Spindler et al., 2018 | ||||||||||||
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Ascendonanus is a genus of the extinct early synapsids - Family varanopidae . Their relatively small, lizard -like representatives lived in the Early Permian (borderline sakmarian / Artinskian ) before about 290 million years ago in what is now Central Europe . The only species described so faris Ascendonanus nestleri from the Petrified Forest of Chemnitz .
etymology
The generic name Ascendonanus is composed of the Latin words ascendo , meaning 'to climb, to climb' and nanus for 'dwarf'. It refers to the small body size and the fact that the representatives of the type species assume a tree-climbing way of life (see below ). The epithet of the single and type species honors Knut Nestler from Chemnitz, who died in 2016 and was a volunteer excavator, sponsor and friend of the Natural History Museum in Chemnitz for many years.
features
For the slender, almost triangular, hardly ornamented skull of Ascendonanus , the following diagnostic features are given in the first description : large eye socket; small external nostril; long lacrimale; low maxillary; Frontal only marginally involved in the outline of the eye socket; Supratemporale long, slender and with the squamosum forming a rudimentary ear slit (squamosal bay). The dentition is de facto homodontic and the teeth are slender, slightly curved or straight and not jagged. The transverse process of the pterygoid is equipped with a single row of teeth. The hyoid is shorter than that of other varanopids. A special feature set " Lid - ossicles is" the (posterior) at the top of the orbit of two copies are handed. Such ossification of the skin (osteoderms) of the upper eyelid was only known from a few temnospondyles , but not from amniotes , until the discovery of Ascendonanus . On the other hand, there are no osteoderms on the trunk. The traditional skin prints (see below ) show a regular scale pattern that roughly corresponds to that of recent reptiles .
The body of Ascendonanus is slender and elongated, and the number of vertebrae that lie between the head and the pelvis (presacral vertebrae) is unusually high at 34 (common with basal amniotes is around 25). The head-to-tail length of the traditional, all safely adult individuals is approx. 40 cm, with the rearmost tail ends missing. The trunk is longer than the hind limbs. Front and rear limbs are roughly the same length. The long bones of the limbs are slender. The ectepicondylar foramen, a small opening on the outer (medial) side of the (distal) joint head of the humerus facing away from the trunk or towards the ulna and radius , is present. The olecranon, an extension protruding beyond the joint and a muscle attachment at the proximal end of the ulna (“elbow”) pointing towards the trunk, is reduced. The front and rear feet are relatively large for a basal synapsid. The tarsal bones ( astragalus and calcaneus ) are slender. The arterial passage in the tarsus (English perforating foramen ) is completely in the astragalus. The phalanges are generally slender and the terminal phalanges are more curved than in all known basal synapsids. The reconstructed phalangeal formulas are 3-4-5-6-? 4 for the front feet and 3-4-5-6-5 for the hind feet.
Fossillocality, Conservation, and Paleoecology
All five known specimens of the genus (at the same time all five known specimens of the A. nestleri type ) * were discovered between 2009 and 2011 in a fossil locale in the Zeisigwald tuff of the Leukersdorf formation of the Vorerzgebirgs basin in the city of Chemnitz . All specimens have been handed down in an anatomical context (articulated) as well as with shadow and impression-like preservation of soft tissues. Ascendonanus is therefore the geologically oldest synapsis and one of the oldest amniotes in the fossil record with such preservation. However, through diagenetic processes and (sub) recent weathering, anatomical details of the skeleton have been more or less blurred. The specimens were embedded in the volcanic sedimentary rock together with silicified tree trunks, leaves and fruit stalks of plants as well as the remains of terrestrial arthropods ( millipedes , spiders , scorpions ) .
The fossil-bearing tuff layers are integrated in partly paleopedogenetically modified alluvial red sediments of the Leukersdorf formation. The traditional flora and fauna as well as sedimentology and geochemistry of deposits can be a ( sub ) tropical forest, a seasonal change from rain and dry seasons was subjected as Paleoenvironment close. The relatively small growth of Ascendonanus , its approximately equally long limbs and its large feet with the sometimes very long, up to 6-jointed fingers or toes and the strongly curved terminal phalanges indicate that it was a tree dweller . Such a way of life was not known from early Permian synapsids until then. Presumably, the animals fell from trees during a volcanic eruption, stunned or killed by volcanic gases ( carbon monoxide or high doses of carbon dioxide, for example) and were then buried under volcanic ash .
Systematics
Recesses in and / or different coloring on the posterior side wall of the skull (temple region) of the fossil specimens of Ascendonanus indicate the presence of a synapsid- typical temporal window . With the ventral keel of the anterior trunk vertebrae and the enlarged back (dorsal) part of the ilium ( iliac blade ), the ascendonanus shows further synapsid-typical features. In the results of a comprehensive cladistic analysis , which were published together with its first description, Ascendonanus appears within the Eupelycosauria ( Varanopidae + Ophiacodontidae + Edaphosauridae + Sphenacodontidae + Therapsiden ) as a basal Varanopide in a sister group relationship with Apsisaurus from the Lower Permian of North Texas. The common clade of Ascendonanus and Apsisaurus forms the sister group of all other Varanopids.
Web links
- On a treasure hunt in Chemnitz: Slusia - video from March 30, 2011 on the YouTube channel of the Chemnitz Natural History Museum, which shows pictures of the excavations in which the specimens of Ascendonanus were found and contains explanations of the preparation of the pieces in the Natural History Museum Schleusingen
literature
Unless otherwise specifically referenced, the entire article is based on:
- Frederik Spindler, Ralf Werneburg, Joerg W. Schneider, Ludwig Luthardt, Volker Annacker, Ronny Rößler: First arboreal 'pelycosaurs' (Synapsida: Varanopidae) from the early Permian Chemnitz Fossil Lagerstätte, SE Germany, with a review of varanopid phylogeny. PalZ - Paleontological Journal. Vol. 92, No. 2, 2018, pp. 315–364, doi: 10.1007 / s12542-018-0405-9 (alternative full text access : ResearchGate ).
Individual evidence
- ↑ For more detailed information on lithologies and facies of the sequence see: Ronny Rößler, Jörg W. Schneider, Ralf Werneburg: The petrified forest of Chemnitz - A snapshot of an Early Permian ecosystem preserved by explosive volcanism. Pp. 211–222 in: Florian Witzmann, Martin Aberhan (Eds.): Centenary meeting of the Paläontologische Gesellschaft - programs, abstracts, and field guides. 24.09. - 29.09.2012, Museum für Naturkunde Berlin. TERRA NOSTRA - Writings of the GeoUnion Alfred Wegener Foundation, 2012, doi: 10.23689 / fidgeo-2034 (complete conference proceedings for download)
- ↑ For details on the location and the excavations see u. a. Ronny Rößler, Volker Annacker, Ralph Kretzschmar, Sandra Mehlhorn: On a treasure hunt in Chemnitz - Scientific excavations '09. Publications of the Museum für Naturkunde Chemnitz. Vol. 32, 2009, pp. 25–26 ( ResearchGate )
- ↑ Ludwig Luthardt, Ronny Rößler, Joerg W. Schneider: Palaeoclimatic and site-specific conditions in the early Permian fossil forest of Chemnitz - Sedimentological, geochemical and palaeobotanical evidence. Palaeogeography, Palaeoclimatology, Palaeoecology. Vol. 441, No. 4, 2016, pp. 627-652, doi: 10.1016 / j.palaeo.2015.10.015