Ronzotherium

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Ronzotherium
Skull of Ronzotherium filholi

Skull of Ronzotherium filholi

Temporal occurrence
Late Eocene to Oligocene
37.7 to 23.3 million years
Locations
Systematics
Higher mammals (Eutheria)
Laurasiatheria
Unpaired ungulate (Perissodactyla)
Rhinocerotoidea
Rhinoceros (Rhinocerotidae)
Ronzotherium
Scientific name
Ronzotherium
Aymard , 1854

Ronzotherium is one of the earliest, now extinct, representatives of the rhinos in Eurasia , who lived from the late Eocene to the end of the Oligocene 37 to 23 million years ago. The rhinoceros genus was first detected in Europe from around 33 million year old Oligocene layers. It was a fairly large representative of the rhinos for the time, but is largely only known from fragmented finds. The forefeet with four toes each, which Ronzotherium placed next to the primitive rhinos, was characteristic.

features

Ronzotherium was a medium-sized to large, but rather slender rhinoceros, the smaller members of which weighed around 1 t, while larger ones could reach a body weight of 1.7 to 1.9 t. However, the genus is largely only known through bone and dentition fragments. The relatively slender limbs, which ended in four rays on the forefoot ( tetradactyl ) and three rays on the hind foot ( tridactyl ), were striking . As with most odd-toed ungulates, the middle, third ray ( metapodium III in each case ) was particularly pronounced , with that of the forefoot over 19 cm long and that of the rear foot up to 16 cm long.

Lower jaw of Ronzotherium

A nearly complete lower jaw measured about 57 cm in length. The strongly developed symphysis extended to the end of the second premolar . There were two pairs of incisors in the upper jaw that were relatively small. In contrast, the lower jaw had only one pair of vaginal teeth, the I2, which was typically pointed forward for rhinos, conical in shape and had a teardrop-shaped cross-section. The tooth length was up to 8.5 cm. One canine was not developed, and there was a large diastema to the rear row of teeth . In adult animals, the molars comprised three premolars and three molars per mandibular arch - in the upper jaw the anterior premolar may have also been formed - with the row of teeth increasing in size towards the back. The anterior premolar was only 2.5 cm long, while the posterior molar was over 7 cm long. In general, the molars had a low ( brachyodontic ) crown, and the posterior premolars were partially molarized and thus resembled the molars. The chewing surfaces had two clearly twisted enamel folds , but their structure was rather primitive.

Fossil finds

Ronzotherium fossils have been found in large parts of Eurasia . In Asia it has been found, among other things, from the Ergiline-Dzo formation in what is now Mongolia , the finds date to the Upper Eocene . Other finds come from the Linxia Basin in the Chinese province of Gansu , but they can be assigned to the late Oligocene . In addition to the eponymous site Ronzon in France with the lower jaw discovery from 1854, two sites from the northeastern urban area of Marseille (Saint-Henri and Saint-André), which are of a late Oligocene age, are important fossil sites in Europe . Around 50 bone and tooth fragments come from here, including several lower jaw fragments and a partially preserved upper jaw. Only a few kilometers away from the town of Les Milles, near the city of Aix-en-Provence , there are almost a dozen other bone fragments, including an almost complete lower jaw. Several sites are known from Central Europe , most of which belong to the molasse basin of the northern Alpine foothills . The finds by Bressaucourt and Kleinblauen in north-western Switzerland deserve special mention , including the lower jaw of a juvenile animal, which is one of the earliest rhino records in Europe. From Rickenbach , also in Switzerland, 35 fossil remains of the skull and body skeleton were reported; This location is one of the type localities for faunal remains from the Late Oligocene and at the same time one of the spätesten occurrence of Ronzotherium . From Germany include the tooth finds from the open pit Espenhain south of Leipzig (Saxony) emphasize that the unteroligozänen Phosphoritknollenhorizont of Böhlen Formation originate.

Paleobiology

Above all, the later members of Ronzotherium , who appeared in western Eurasia, were adapted to a rather dry climate with an annual average temperature of around 20 ° C, which could be determined on the basis of isotope tests on teeth from Rickenbach. They lived in partly open, savannah-like landscapes that were created in the course of the Grande Coupure event. Most niederkronigen teeth give a soft vegetable diet preferring ( browsing ) herbivores on, but due to the prevailing landscapes also a certain amount of hard grass food can not be excluded.

Systematics

Internal systematics of Eurasian Aceratheriini according to Tissier et al. 2020
  Rhinocerotidae  

 Trigonias


   


 Uintaceras


   

 Epiaceratherium



   

 Teletaceras


   

 Penetrigonias


   


 Amphicaenopus


   

 Ronzotherium



   


 Molassitherium


   

 Diceratherium


   

 Subhyracodon




   

 Phylogenetically younger rhinos








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Ronzotherium is a genus of the rhinoceros family . Within the rhinos it belongs to the "core group" of this odd ungulate group , from which the younger representatives can be derived. Ronzotherium occurs in Eurasia in the early Oligocene 37 million years ago, just as early as its relative Guixia . However, both rhinoceros show different relationships due to tooth morphological deviations: Ronzotherium is closer to Trigonias and Penetrigonias , possibly also Amphicaenopus , while Guixia has similarities to Teletaceras .

The following types of Ronzotherium are recognized today:

Originally, however, many more species were accepted. The R. orientale from Mongolia described by Bolat Demberelyin Dashzeveg in 1991 using an almost complete and a more fragmented lower jaw is synonymous with R. brevirostre . Other forms, such as R. osborni and R. gaudryi, are now assigned to the genus Eggysodon , which, as a member of the Hyracodontidae, is only a close relative of the rhinos.

The genus Ronzotherium had a Eurasian distribution with a focus on the northern area. It has its earliest occurrence in Asia , where it was first recorded in the late Eocene 37 million years ago. The rhinoceros representative appears in Europe for the first time after the Grande Coupure event of the early Oligocene a little more than 33 million years ago, roughly at the same time as Epiaceratherium . The tetradactyled hands refer Ronzotherium to the primeval rhinos that persisted in Eurasia up to the Upper Miocene , but since the Lower Miocene have been gradually replaced by those with three toes on the forefoot. In North America , these four-toed rhinos died out at the beginning of the Oligocene and were completely replaced by rhinos with three-pronged hands.

The term Ronzotherium was first mentioned by Auguste Aymard in 1854 and is based on a rear part of a lower jaw of Ronzon near Le Puy-en-Velay ( Haute-Loire department ; France). However, it wasn't until Henry Filhol more than twenty-five years later, in 1881, that this fossil was described in more detail. Originally viewed as the remainder of an adult animal with the three remaining last premolars and three molars, it was later recognized that this fossil belonged to a young animal in which the last molar had not yet erupted, leaving the entire row of teeth the four premolars and the first two Molars included. The generic name Ronzotherium refers on the one hand to the locality Ronzon, while θήριον ( thêrion "animal") is of Greek origin.

Individual evidence

  1. ↑ a b c Damien Becker: Earliest record of rhinocerotoids (Mammalia: Perissodactyla) from Switzerland: systematics and biostratigraphy. Swiss Journal of Geosciences 102, 2009, pp. 489-504
  2. ↑ a b c d e Bastien Mennecart, Laureline Scherler, Florent Hiard, Damien Becker and Jean-Pierre Berger: Large mammals from Rickenbach (Switzerland, reference locality MP29, Late Oligocene): biostratigraphic and alaeoenvironmental implications. Swiss Journal of Geosciences 131 (1), 2012, pp. 161-181
  3. ↑ a b Tao Deng: Late Cenozoic environmental changes in the Linxia basin (Gansu, China) as indicated by cenograms of fossil Mammals. Vertebrata Palasiatica 47 (4), 2009, pp. 282-298
  4. ↑ Oldrich Fejfar and Thomas M. Kaiser: Insect bone-modification and paleoecology of Oligocene mammal-bearing sites in the Doupov Mountains, northwestern Bohemia. Paleontologia Electronica 8 (8A), 2005, pp. 1-11
  5. ↑ a b Bernard Ménouret and Claude Guérin: Diaceratherium massiliae nov. sp. des argiles oligocènes de Saint-André et Saint-Henri à Marseille et de Les Milles près d'Aix-en-Provence (SE de la France), premier grand Rhinocerotidae brachypode européen. Geobios 42, 2009, pp. 293-327
  6. ↑ a b c d Pierre-Olivier Antoine, Stéphane Ducrocq, Laurent Marivaux, Yaowalak Chaimanee, Jean-Yves Crochet, Jean-Jacques Jaeger, and Jean-Loup Welcomme: Early rhinocerotids (Mammalia: Perissodactyla) from South Asia and a review of the Holarctic Paleogene rhinocerotid record. Canadian Journal of Earth Sciences 40, 2003, pp. 365-374
  7. ↑ Deng Tao: Linxia Basin: An Ancient Paradise for Late Cenozoic Rhinoceroses in North China. Paleomammalogy 24 (2), 2010, pp. 103-106
  8. ↑ a b Undine Uhlig and Madelaine Böhme: A new Rhinocerotidae (Mammalia) from the Lower Oligocene of Central Europe (Espenhain near Leipzig, NW Saxony, Germany). New yearbook for geology and palaeontology treatises, Stuttgart 220, 2001, pp. 83–92
  9. ↑ E. Emery, D. Becker and J.-P. Berger: The macromammalian fauna (Ungulata) of Rickenbach (Solothurn), Late Chattian, Swiss Molasse: biostratigraphy, paleoecology and paleoclimate. Abstracts 2nd Swiss Geoscience Meeting, Lausanne, 2004 ( [1] ; PDF; 124 kB)
  10. ↑ Jérémy Tissier, Pierre-Olivier Antoine and Damien Becker: New material of Epiaceratherium and a new species of Mesaceratherium clear up the phylogeny of early Rhinocerotidae (Perissodactyla). Royal Society Open Science 7, 2020, p. 200633, doi: 10.1098 / rsos.200633
  11. ↑ Kurt Heissig: The American genus Penetrigonias Tanner & Martin, 1976 (Mammalia: Rhinocerotidae) as a stem group elasmothere and ancestor of Menoceras Troxell, 1921. Zitteliana A 52, 2012, pp. 79-95
  12. ↑ Demberrlyin Dashzeveg: Hyracodontids and rhinocerotids (Mammalia, Perissodactyla, Rhinocerotoidea) from the Paleogene of Mongolia. Palaeovertebrata 21 (1/2), 1991, pp. 1-84
  13. ^ Qiu Zhan Xiang and Wang Ban Yue: Allacerops (Rhinocerotoidea, Perissodactyla). its discovery in China and its systematic position. Vertebrata Palasiatica 37 (1), 1999, pp. 48-61
  14. ^ A. Aymard: Des terrains fossilifères du bassin supérieur de la Loire. Comptes Rendus des Séances de l'Académie des Sciences 38, 1854, pp. 673–677 ( [2] )
  15. ^ Henry Fairfield Osborn: Phylogeny of the rhinoceroses of Europe. Rhinoceros contributions, No. 5. Bulletin American Museum of Natural History 13, 1900, pp. 229-2676
  16. ↑ Otto Abel: Critical studies on the paleogenic rhinocerotids of Europe. Treatises of the Imperial and Royal Geological Reichsanstalt 20 (3), 1910, pp. 1–52

Web links

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