Hemimachairodus

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Hemimachairodus
Temporal range: Pleistocene
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Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Feliformia
Family: Felidae
Subfamily:† Machairodontinae
Genus:† Hemimachairodus
Koenigswald, 1974
Type species
Hemimachairodus zwierzyckii
(von Koenigswald, 1934)
Synonyms
  • Epimachairodus zwierzyckiivon Koenigswald, 1934
  • Homotherium zwierzyckiisensu Kurtén, 1962

Hemimachairodus is an extinct genus of machairodontine (sabre-toothed) cat with only one species, Hemimachairodus zwierzyckii, known from only a few fossils from the Pleistocene of Java. Other fossils attributed to Hemimachairodus sp. are known from the Villafranchian (late Pliocene to early Pleistocene) of Tajikistan.

Contents

Discovery and naming

The species was originally described in 1934 by German palaeontologist Gustav Heinrich Ralph von Koenigswald under the name Epimachairodus zwierzyckii. [1] He referred to it again by that name in 1940. [2] A 1962 paper by Bjorn Kurtén referred to it as Homotherium zwierzyckii, stating that its homotheriine affinities were unmistakable, although he allowed it might also belong to the homotheriine genus Dinobastis instead. [3]

In 1974, Koenigswald described more fossils that he assigned to the species, and referred it to a new genus Hemimachairodus. No etymology for the genus name was given. He assigned Hemimachairodus to the subfamily Machairodontinae. [4]

In 1988, Soviet paleontologists described fossils from the Villafranchian-aged Kuruksay (Lagernaja) locality in Tajikistan that they assigned to Hemimachairodus sp. [5] Further study of Plio-Pleistocene carnivorans touched on its presence in 1989, [6] and Scharapov included a section on Hemimachairodus in his 1996 review of machairodontine fossils from the Tajikistan. [7]

Etymology

The specific epithet was given in honor of the Polish geologist Józef Zwierzycki. [8] The genus name seems to be a combination of the Greek ἡμι/hēmi meaning "half", and Machairodus .[ original research? ]

Description

Koenigswald's 1974 diagnosis of Hemimachairodus noted the complete reduction of the third premolar, and serrations on the upper canine teeth being limited to the inner edge. [4] Scharapov's 1996 review noted that Hemimachairodus was similar to Homotherium in size and proportions, and only differed by the absence of the third premolar and the notching on inner side of the upper canine. [7]

The holotype of Hemimachairodus zwierzyckii is a partial left mandibular ramus, retaining the first incisor, the canine, and the fourth premolar, after which it is broken. Koenigswald in 1974 described it as having a weak mental process and a strongly developed mental crest. The mandible itself is slender, with a 46mm diastemata. It was recovered from Sangiran in central Java. [4]

From Sangiran, Koenigswald (1974) also described a second partial jaw fossil, broken about 1cm behind the molar and 2cm in front of the premolar and retaining both teeth; one tip and one complete lower canine; and two fragments of an upper canine tooth. And from the Djetis Beds Modjokerto in eastern Java, a fragment of a mandible retaining a premolar and the front half of a molar. [4] H. zwierzyckii was estimated by one study to have weighed about 130 kilograms (290 lb). [9]

Palaeoenvironment

Java

The Sangiran Dome locality in Java, Indonesia from which von Koenigswald collected the fossils spans over a million years, and he did not record the stratigraphic backgrounds of his finds. Volmer et al. in 2016 estimated that von Koenigswald's machairodontine fossils came from the Ci Saat or Kedung Brubus faunal units, or possibly the Trinil H.K. faunal unit between them, which collectively date to the Early to Middle Pleistocene; [9] a previous paper in 2001 had placed Hemimachairodus in the Trinil H.K. faunal unit. [10] Other large carnivorans from the same deposits the tiger, fellow machairodontine Homotherium latidens, and the canid Megacyon merriami , all which H. zwierzyckii likely competed with for prey, and the intense competition may have led to its extinction. [9] Other mammals known from the Sangiran locality include rodents, wild pigs, tapirs, muntjacs, deer, rhinoceros, the antelope Duboisia santeng , and the proboscidean Stegodon trigonocephalus. [10]

Tajikistan

The Kuruksaj locality, meanwhile, is estimated to be 2.4-2.4 million years of age (late Pliocene, European Land Mammal Unit MN17). Fossils of both forest and plains-dwelling mammals have been found there, including leporines, the rodents Hystrix and Promimomys , the monkey Paradolichopithecus , canids Nyctereutes megamastoides and Canis kuruksaensis , hyaenas Chasmaporthetes and Pachycrocuta , an indeterminate bear, two different proboscideans, the rhinoceratid Dicerorhinus , the horse Equus stenonis , the camelid Paracamelus , giraffids Sogdianotherium and Sivatherium , and several species each of cervids (deer) and bovids. [11]

References

  1. ↑ von Koenigswald, G. H. R. (1934). "Zur Stratigraphie des javanischen Pleistocan" [On the stratigraphy of the Javanese Pleistocene]. De Ingenieur in Nederlandsch Indie (in German). 1 (11): 190. hdl:1887.1/item:2451806.
  2. ↑ von Koenigswald, D. H. R. (1940). "Neue Pithecanthropus-Funde 1936-1938; Eine Beitrag zur Kenntnis der Prae-Hominiden". Wetenschapplijke Mededeelingen Dienst van Mijnbouw NederlandscheIndië. 28: 57.
  3. ↑ Kurtén, B. (1962). "The sabre-toothed cat Megantereon from the Pleistocene of Java". Zoologische Mededelingen. 38 (6): 101–104.
  4. 1 2 3 4 von Koenigswald, G.H.R. (1974). "Fossil mammals of Java part 6: Machairodontinae from the lower Pleistocene of Java". Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen Series B Physical Sciences. 77 (4): 267–273. INIST   PASCALGEODEBRGM7520066100.
  5. ↑ Sotnikova, M. V. (1988). Биестратиграфия поэднего плиоцена-раннего плейстоцена Таджикистана по фауне млекопитаюших[Biostratigraphy of Late Pliocene–Early Pleistocene of Tadzhikistan (based on mammalian fauna)] (in Russian). ISBN   5020033375.
  6. ↑ Sotnikova, Marina V. (1989). Хищные млекопитающие плиоцена–раннего плейстоцена: стратиграфическое значение[Late Pliocene-Early Pleistocene Carnivora: Stratigraphic Significance] (in Russian). Alexander Doweld. pp. 11, 83. ISBN   5020045950. ISSN   0002-3272.
  7. 1 2 Scharapov, Scharif (1996). "Säbelzahnkatzen (Mammalia: Carnivora: Machairodontinae) aus dem späten Känozoikum Tadschikistans" [Saber-toothed cats (Mammalia: Carnivora: Machairodontinae) from the late Cenozoic of Tadzhikistan]. Senckenbergiana Lethaea (in German). 76 (1–2): 251–252, 255. doi:10.1007/BF03042851.
  8. ↑ Chrząstek, Alina; Górecka-Nowak, Anna; Kryza, Ryszard (2014). "Józef Zwierzycki, a great geologist of the 20th century (reminiscence 50 year after decease)". Geologia Sudetica. 42 (3–189): 172.
  9. 1 2 3 Volmer, Rebekka; Hertler, Christine; van der Geer, Alexandra (1 January 2016). "Niche overlap and competition potential among tigers (Panthera tigris), sabertoothed cats (Homotherium ultimum, Hemimachairodus zwierzyckii) and Merriam's Dog (Megacyon merriami) in the Pleistocene of Java". Palaeogeography, Palaeoclimatology, Palaeoecology. 441: 901–911. Bibcode:2016PPP...441..901V. doi:10.1016/j.palaeo.2015.10.039. hdl: 10795/3286 .
  10. 1 2 Aziz, F. (2001). "Pleistocene Fauna of Sangiran and Other Hominid Sites in Java". Sangiran: Man, Culture, and Environment in Pleistocene Times.
  11. ↑ Takai, Masanaru; Maschenko, Evgeny N.; Nishimura, Takeshi D.; Anezaki, Tomoko; Suzuki, Tomoki (2008). "Phylogenetic relationships and biogeographic history of Paradolichopithecus sushkini Trofimov 1977, a large-bodied cercopithecine monkey from the Pliocene of Eurasia". Quaternary International. 179 (1): 108–109. Bibcode:2008QuInt.179..108T. doi:10.1016/j.quaint.2007.10.012.
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