Stahleckeria
| Stahleckeria | ||||||||||||
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Drawing life reconstruction of Stahleckeria potens |
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| Ladinium ( Middle Triassic ) | ||||||||||||
| 242 to 235 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Stahleckeria | ||||||||||||
| Huene , 1935 | ||||||||||||
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Stahleckeria is a large genus of therapsids from the extinct group Dicynodontia . Fossil remains of this genus are known from the Central Triassic (approx. 240 mya ) Santa Maria Formation of the Paraná Basin in the Brazilian state of Rio Grande do Sul and from the approximately equally old Omingonde Formation of the Waterberg Basin in Namibia. The only currently recognized species is Stahleckeria potens .
Taxonomic history
The type material of the type species Stahleckeria potens , three skulls and numerous postcrania , was discovered at the end of the 1920s by Rudolf Stahlecker , a student of the famous German vertebrate paleontologist Friedrich Baron Hoyningen, called Friedrich von Huene , on a fazenda in the parish of São Pedro do Sul (fossil-ocality Chiniquá ) excavated in southern Brazil. The first description of the genus and species by von Huene was published in 1935. He chose the generic name Stahleckeria in honor of the finder.
The also very important American paleontologist Alfred Romer and his Brazilian colleague Llewellyn Ivor Price described another species in 1944, Stahleckeria lenzii , based on an incomplete skull and some postcrania from the neighboring locality of Candelária to the east. This species was moved to the specially established genus Barysoma in 1965 , but was synonymous with Stahleckeria potens in 1993 .
The same author who made this synonymization described a new species, Stahleckeria impotens , based on a relatively small skull and several postcranial elements from a locality near Cachoeira do Sul in 2002 and also assigned it some pieces from the type locality. However, an immediate (2005) re-examination of this material revealed that it is likely to be non-adult individuals of Stahleckeria potens . Thus, Stahleckeria potens is the only generally accepted species.
In 2013 the first discoveries of Stahleckeria outside the Santa Maria Formation and beyond South America were reported. The skull as well as some postcrania came from localities in the Omingonde Formation on Waterberg in northern Namibia.
features
One of the most striking features of Stahleckeria is its size. The living animals were about 3 m long and had a stocky, massive habit, similar to today's large mammals such as rhinos and hippos . The skeleton shows numerous adaptations to a high body weight, especially very short, thick arm and leg bones. The rib cage is voluminous and barrel-shaped.
The skull shows the typical features of the Dicynodontier, with principally toothless jawbones and a large premaxillary drawn down at the tip of the snout. In living animals, the premaxillary and the opposite part of the dental probably had sharp-edged horn sheaths that functioned as "incisors". The maxillary "tusks" which are typical for many dicynodontic animals and which give the group its name, which are also particularly pronounced in Dinodontosaurus , a genus that also occurs in the Santa Maria formation, are absent in Stahleckeria . The pre-orbital skull is both relatively high and relatively wide. It tapers towards the front (rostral), but the tip of the snout is rather blunt. The lacrimale is not involved in the outline of the outer nostril. The jugale is small and forms the lower (ventral) edge of the eye socket. The upper (dorsal) part of the maxillary does not reach up to the back of the snout. The posterior part of the maxillary protrudes relatively far into the anterior section of the lower temporal arch ("zygomatic arch") like a wedge. The rest of the lower temporal arch is formed exclusively by the squamosum , as is a large part of the remaining posterior part of the dermal cranial roof, including the lateral walls of the occiput. The postorbital is large and forms a postorbital arch, the ventral end of which is in contact with the anterior portion of the lower temporal arch. The pineal foramen lies largely within the posterior parts of the frontalia, so that the anterior parts of the parietals are only involved in the posterior end of the foramen, in contrast to the closely related genus Ischigualastia , in which the pineal foramen is predominantly framed by the parietals. The sagittal ridge (intertemporal ridge, parietal ridge) is weak, low and relatively wide.
Way of life
Stahleckeria shows typical characteristics of a large herbivore. The ecological niche it occupied may have resembled that of today's large, heavy herbivorous mammals. Accordingly, when fully grown, she only had to fear the largest carnivores in her life.
The diet probably consisted mainly of relatively soft plant material. Their occipital index, a value that is determined from the proportions of the skull and the distances between the attachment points of the neck muscles on the occiput and the occiput condyle , suggests that the individuals of Stahleckeria preferred to graze on low vegetation.
Systematics
Stahleckeria is a type taxon of the subfamily Stahleckeriinae and the family Stahleckeriidae . According to a relationship analysis from 2013, the latter are the most strongly derived group of the Kannemeyeriiformes , a group of large, heavily built, purely Triassic dicynodont animals. With its size and habitus, Stahleckeria is a larger but typical representative of the Kannemeyeriiformes.
meaning
In terrestrial vertebrate biostratigraphy , Stahleckeria is a distinctive taxon of the Dinodontosaurus Assemblage Zone , which in turn characterizes deposits of the upper Middle Triassic (Ladinium). The occurrence of Stahleckeria in the Omingonde formation confirmed the assumption that this unit, contrary to traditional opinion, is Ladin instead of at most Aniseed in age. In addition, this find once again confirmed the close geographical relationship between southern Africa and South America in the early Mesozoic era (cf. → Pangea , → Gondwana ).
Museum pieces
A skeleton reconstruction based on the type material collected in the 1920s is exhibited in the paleontological collection of the Museum of the University of Tübingen .
Although it is located near the type locality of Stahleckeria , the Paleontological and Archaeological Museum Walter Ilha in São Pedro do Sul on the Paleorrota did not have a corresponding exhibit for a long time. This only changed in April 2009, when employees of the Museum of the University of Tübingen handed over the replica of a Stahleckeria skull to the Walter Ilha Museum in a festive setting .
Individual evidence
- ^ Friedrich von Huene: The fossil reptiles of the South American Gondwanaland. Results of the dinosaur excavations in southern Brazil in 1928/29. Delivery 1 - Anomodontia. CH Beck'sche Verlagsbuchhandlung, Munich 1935.
- ^ Alfred S. Romer, Llewellyn I. Price: Stahleckeria lenzii , a giant Triassic Brazilian dicynodont. Bulletin of the Museum of Comparative Zoology. Vol. 93, 1944, pp. 463-491 ( BHL ).
- ^ A b Christopher Barry Cox: New Triassic Dicynodonts from South America, their Origin and Relationships. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. Vol. 248, No. 753, 1965, pp. 457-514, doi : 10.1098 / rstb.1965.0005 ( Open Access ).
- ↑ Spencer G. Lucas: Barysoma lenzii (Synapsida: Dicynodontia) from the Middle Triassic of Brazil, a synonym of Stahleckeria potens. Journal of Paleontology. Vol. 67, No. 2, 1993, pp. 318-321, doi : 10.1017 / S0022336000032285 (alternatively: JSTOR 1306004 ).
- ↑ a b c Spencer G. Lucas: A new dicynodont from the Triassic of Brazil and the tetrapod biochronology of the Brazilian Triassic. In: Andrew B. Heckert, Spencer G. Lucas (Eds.): Upper Triassic stratigraphy and paleontology. New Mexico Museum of Natural History and Science Bulletin. Vol. 21, 2002, pp. 131-142 ( online ).
- ↑ a b c d Cristina Vega-Dias, Michael W. Maisch, Cibele Schwanke: The taxonomic status of Stahleckeria impotens (Therapsida, Dicynodontia): redescription and discussion of its phylogenetic position. Revista Brasileira de Paleontologia. Vol. 8, No. 3, 2005, pp. 221-228 ( PDF 1.7 MB).
- ↑ a b Fernando Abdala, Claudia A. Marsicano, Roger MH Smith, Roger Swart: Strengthening Western Gondwanan correlations: A Brazilian Dicynodont (Synapsida, Anomodontia) in the Middle Triassic of Namibia. Gondwana Research. Vol. 23, No. 3, 2013, pp. 1151–1162, doi : 10.1016 / j.gr.2012.07.011 (alternative full text access : ResearchGate ).
- ↑ Mikhail V. Surkov, Michael J. Benton: Head Kinematics and Feeding Adaptations of the Permian and Triassic Dicynodonts. Journal of Vertebrate Paleontology. Vol. 28, No. 4, 2008, pp. 1120-1129, doi : 10.1671 / 0272-4634-28.4.1120 (alternatively: JSTOR 20491043 ).
- ^ Christian F. Kammerer, Jörg Fröbisch, Kenneth D. Angielczyk: On the Validity and Phylogenetic Position of Eubrachiosaurus browni , a Kannemeyeriiform Dicynodont (Anomodontia) from Triassic North America. PLoS ONE. Vol. 8, No. 5, 2013, e64203, doi : 10.1371 / journal.pone.0064203 .
- ↑ Stahleckeria potens : Skull handover in São Pedro do Sul. Entry from April 6, 2009 on Tübingen excursion to Brazil - field exercises on tropical biodiversity in Brazil . Blog from employees of the University of Tübingen
- ↑ Gazeta Regional, April 11, 2009, pp. 1, 2, 5 and 6. ( PDF ; 930 kB)
Web links
- The Paleobiology Database: Stahleckeria