Haramiyida

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Haramiyida
Temporal occurrence
Upper Triassic to Lower Cretaceous
210 to 140 million years
Locations
Systematics
Amniotes (Amniota)
Synapsids (Synapsida)
Mammals (mammalia)
Theriiformes
Allotheria
Haramiyida
Scientific name
Haramiyida
Hahn , Sigogneau-Russel & Wouters , 1989

The Haramiyida are a group of extinct mammals , which are mainly documented by sparse tooth and jaw finds and lived in the Triassic and Jurassic ages.

General

The oldest finds come from the Upper Triassic, they are around 210 million years old and, along with Adelobasileus cromptoni, are among the oldest known mammal fossils. The most recent finds of this group are dated to the Upper Jura. The fossils discovered so far consist mainly of remains of the jaws and teeth. Finds have been made in Europe , Greenland , Africa , China and the USA.

Knowledge about these animals is mainly limited to the facts that can be deduced from the teeth. The molars are relatively large and have numerous cusps, more precisely three large ones on one side and five small ones on the other side of the tooth. Between the cusps there was a depression into which the cusps of the opposing teeth were inserted.

The relationships between the Haramiyida and other groups of mammals were unexplained for a long time, mostly they were viewed as a very original side branch. Due to the similarities in the structure of the teeth, the Haramiyida were previously considered to be the ancestors of the Multituberculata , a once widespread group of mammals from the Jurassic to the Eocene , which is also characterized by numerous cusps on the molar teeth. Haramiyida and Multituberculata have been grouped together in a common taxon, Allotheria . The structure of the jaw, which has been known since the Haramiyavia discoveries, still shows very primeval features. Since the multituberculata showed stronger similarities in their jaw structure to today's mammals, the evolution of the jaw should be a convergent evolution. The majority of today's researchers consider this to be unlikely, so that today we tend to assume that the similarities in the structure of the teeth are purely external. Most likely, the Haramiyida are an isolated early side branch in the development of mammals.

The genera and species

  • Individual teeth found in various countries in Western Europe from the times of the Upper Triassic and Lower Jurassic have been classified into the genus Haramiya and Thomasia . More recent finds have shown that these are only the upper ( Haramiya ) and lower ( Thomasia ) molars of the same genus, for reasons of priority (the older name is the valid one in this case) the finds are now in Thomasia (named after Oldfield Thomas , an eminent mammal researcher).
  • The best-preserved fossils so far are known from Haramiyavia from the Upper Triassic, found in Greenland. In addition to teeth, remnants of the lower jaw and even individual parts of the remaining skeleton were found, which indicate a small, agile animal. Haramiyavia's skull length is estimated to be 4 cm; the teeth suggest a herbivore or omnivore.
  • A single tooth from the Upper Triassic is all that is known of the genus Hypsiprymnopsis .
  • Of the genus Theroteinus , only individual teeth are known that come from France and are dated to the Upper Triassic.
  • Also Mojo is known only from isolated teeth, which in Belgium were found and also come from the Upper Triassic.
  • More recent is the genus Eleutherodon , which is known from England and of which remains were found in China in 2005 . She lived in the middle Jurassic.
  • From two other genera, Millsodon and Kirtlingtonia , individual teeth from the Middle Jurassic were also found in England in 2005.
  • The genus Staffia is the geologically youngest representative of the Haramiyida and the first to be discovered in what was then Gondwana . Dental finds of this genus were made in Tanzania and are dated to the Upper Jurassic.
  • Megaconus from the Central Jurassic of China had high-crowned molars and was adapted to a vegetable diet.
  • In August 2013, Arboroharamiya from northeast China's Tiaojishan Formation was described as a tree dweller. The approximately 160 million year old holotype shows most of the trunk Velcro, parts of the limbs and the jaw and is the largest haramiyid described so far. A phylogenetic analysis showed that Arboroharamiya is in a sister group relationship to the Multituberculata , a group of extinct mammals that showed parallels to rodents in their dimensions, diversity and assumed way of life. In August 2014 Arboroharamiya was assigned to the new taxon Euharamiyida together with three other, newly described tree-dwelling early mammals . The Haramiyida thus become a paraphyletic group, since they consist of genera that are basal to the clade of Euharamiyida and Multituberculata, as well as genera of the Euharamiyida and the Multituberculata that are not part of the Haramiyida.
  • Maiopatagium furculiferum and Vilevolodon diplomylos were described as newly identified species from China in August 2017. Both species had long limbs, toes and fingers, between which there were flat membranes thatenabledthem to glide similar to today's gliding squirrels .
  • Cifelliodon wahkarmoosuch was described in mid-2018, occurred in North America and was the last known survivor of the Haramiyida to live in the Lower Cretaceous.

literature

  • TS Kemp, The Origin & Evolution of Mammals. Oxford University Press, Oxford et al. 2005, ISBN 0-19-850761-5 .

Individual evidence

  1. ↑ Chang-Fu Zhou, Shaoyuan Wu, Thomas Martin & Zhe-Xi Luo: A Jurassic mammaliaform and the earliest mammalian evolutionary adaptations. Nature 500, 163-167 (August 2013) doi: 10.1038 / nature12429
  2. ↑ Xiaoting Zheng, Shundong Bi, Xiaoli Wang & Jin Meng: A new arboreal haramiyid shows the diversity of crown mammals in the Jurassic period. Nature 500, 199-202 (August 2013) doi: 10.1038 / nature12353
  3. ↑ Shundong Bi, Yuanqing Wang, Jian Guan, Xia Sheng, Jin Meng: Three new Jurassic euharamiyidan species reinforce early divergence of mammals. Nature, 2014; Pp. 579-584. doi : 10.1038 / nature13718
  4. ↑ Qing-Jin Meng, David M. Grossnickle, Di Liu, Yu-Guang Zhang, April I. Neander, Qiang Ji, Zhe-Xi Luo: New gliding mammaliaforms from the Jurassic. Nature, 2017. doi : 10.1038 / nature23476
  5. ↑ Adam K. Huttenlocker, David M. Grossnickle, James I. Kirkland, Julia A. Schultz and Zhe-Xi Luo. 2018. Late-surviving Stem Mammal Links the Lowermost Cretaceous of North America and Gondwana. Nature. DOI: 10.1038 / s41586-018-0126-y