Dagbatitherium

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Dagbatitherium
Temporal range: Middle Eocene, 47.8–41.3  Ma
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Proboscidea
Suborder: Elephantiformes
Genus: Dagbatitherium
Hautier et al. 2021
Species:
D. tassyi
Binomial name
Dagbatitherium tassyi
Hautier et al. 2021

Dagbatitherium is an extinct genus of proboscideans. So far a single molar from the phosphate basins of Togo in West Africa has been found. The fossil dates to the Middle Eocene, around 47 million years ago. A striking feature of the tooth are the three pairs of cusps oriented transversely to the longitudinal axis of the tooth. This feature is found in more derived proboscideans, which are grouped in the Elephantiformes. For its age, Dagbatitherium is the earliest member of Elephantiformes to date. Furthermore, it is characterized by a low tooth crown and a humped occlusal pattern. The genus was described in 2021.

Contents

Discovery and naming

The only tooth of Dagbatitherium found so far is from West Africa and was recovered in the Hahotoé-Kpogamé phosphate complex. These are phosphate-bearing deposits formed in a coastal basin. They extend over a length of 30 to 35 km and a width of 2 to 3 km in a northeast-southwest direction between the towns of Dagbati and Aveta in Togo. First explored by drilling in the 1950s, they have been mined economically in large open-pit operations since the 1960s. This requires the removal of up to 30 m thick overlying sediments. The phosphate deposits were formed in a shallow marine environment. In principle, three units can be distinguished, consisting first of 10 to 15 m thick phosphate-bearing marks (Couche 3 and Couche 2), followed by 1 to 8 m thick phospharenites (Couche 1) and about 1 m thick phosphate-bearing clays (Couche 0). Especially the two lower depositional units are very rich in fossils, dominated by remains of sharks and rays. In the phospharenites, however, several bone deposits are also formed with, among others, fossils of whales and manatees. The tooth of Dagbatitherium was found in the basal parts of the phospharenites in the mining area of Dagbati. Numerous minerals of terrestrial origin and pollen indicate a once coastal situation. Accompanying foraminifera were also found. Based on these, an age dating to the Middle Eocene about 46.5 to 44 million years ago could be determined for the deposits. [1] [2] [3] The genus name Dagbatitherium is composed of the name of the locality and the Greek word θηρίον (thērion) for "beast". Together with the genus, the species Dagbatitherium tassyi was erected. The species epithet honors the researcher Pascal Tassy, who devoted his scientific work to the study of proboscideans. [3]

Description

Dagbatitherium is the smallest and oldest representative of the Elephantiformes to date, a group of proboscideans that led to today's elephants. However, only one lower molar is currently known, possibly representing the first or second of the molar row. Its length is 37.5 mm, its width 29.2 mm. The tooth was characterized by its low (brachyodont) dental crown, which is a difference from the higher ones in other early Elephantiformes such as Phiomia or Palaeomastodon . Two distinct pairs of cusps existed on the masticatory surface, oriented transversely to the longitudinal tooth axis. The two lip-sided cusps (protoconid and hypoconid) appeared broader and lower than the tongue-sided ones (metaconid and entoconid). The respective pairs of cusps were divided by a deep pit in the central axis of the tooth. The broad lip-sided cusps caused the tooth crown wall to be more inclined, while the tongue-sided one was steeper. Sharper ridges were sometimes formed on the cusps, causing the bunodont (humped) occlusal surface pattern to tend more toward a bunolophodont (with ridges) one. In addition to the main cusps, individual secondary cusps also occurred. A third pair of cusps joined at the posterior end of the tooth. It thus gave the molar a trilophodont (with three pairs of cusps/groins) appearance. This is a typical characteristic of the Elephantiformes and separates the group from the more primitive proboscideans with bilophodont teeth (with two cusp pairs/groins). In the Deinotheriidae, which also possessed a trilophodont anterior molar, the individual cusp pairs were much more clearly fused into ridges. As another distinctive feature, the tooth in Dagbatitherium ended behind the third cusp pair in a cingulum, a low enamel bulge. In addition, it already exhibited a three-layered enamel pattern, again typical of more derived proboscideans, but absent in some earlier forms. [3]

Classification

Dagbatitherium is an extinct genus of the order Proboscidea. Its trilophodont-built molar places it in the group Elephantiformes, which unites the more modern evolutionary lineages of the proboscideans. In contrast, the Plesielephantiformes (which are paraphyletic) are the most basal representatives of the order, which are characterized by a bilophodont dental structure, i.e. they have only two pairs of cusps or ridges. [4] [5]

Dagbatitherium is considered to be the oldest member of the Elephantiformes known to date. Other forms like Phiomia and Palaeomastodon are much younger and were mostly described from the Late Eocene and Early Oligocene of the Fayyum. Compared to these two, Dagbatitherium was strikingly smaller, had lower tooth crowns, and a more complex enamel pattern. However, a trait that all three forms have in common is a striking bunodont (humped) occlusal surface design. The latter feature contrasts with the sometimes more distinctly lophodont teeth of earlier or contemporaneous members of the Plesielephantiformes, such as Phosphatherium , Numidotherium , or Barytherium , in which the individual cusps of a pair are connected with ridges. In dental structure, Dagbatitherium and other early elephantiforms thus more closely resemble Moeritherium and Saloumia , which form an archaic group of proboscideans that was sometimes considered a lateral branch. Further similarities are found in Eritherium , the most primitive member of the order known to date, which also possessed bunodont grinders. Altogether, however, the relationships of the early proboscideans of the Paleogene are still poorly known. Within the Elephantiformes, Dagbatitherium has not yet been assigned to a specific family. [6] [7] [8] [3]

Below is a phylogenetic tree of early Proboscidea, based on the work of Hautier and colleagues (2021). [3]

   Proboscidea  

  Eritherium

  Phosphatherium

  Daouitherium

  Numidotherium

  Barytherium

  Arcanotherium

  Omanitherium

  Saloumia

  Moeritherium

  Deinotheriidae

  Elephantiformes  

  Elephantimorpha

 Dagbatitherium

Related Research Articles

<span class="mw-page-title-main">Proboscidea</span> Order of elephant-like mammals

Proboscidea is a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. From the mid-Miocene onwards, most proboscideans were very large. The largest land mammal of all time may have been a proboscidean; Palaeoloxodon namadicus was up to 5.2 m (17.1 ft) at the shoulder and may have weighed up to 22 t, almost double the weight of some sauropods like Diplodocus carnegii. The largest extant proboscidean is the African bush elephant, with a record of size of 4 m (13.1 ft) at the shoulder and 10.4 t. In addition to their enormous size, later proboscideans are distinguished by tusks and long, muscular trunks, which were less developed or absent in early proboscideans.

<span class="mw-page-title-main">Molar (tooth)</span> Large tooth at the back of the mouth

The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name molar derives from Latin, molaris dens, meaning "millstone tooth", from mola, millstone and dens, tooth. Molars show a great deal of diversity in size and shape across mammal groups. The third molar of humans is sometimes vestigial.

<span class="mw-page-title-main">Mammutidae</span> Extinct family of mammals

Mammutidae is an extinct family of proboscideans belonging to Elephantimorpha. It is best known for the mastodons, which inhabited North America from the Late Miocene until their extinction at beginning of the Holocene, around 11,000 years ago. The earliest fossils of the group are known from the Late Oligocene of Africa, around 24 million years ago, and fossils of the group have also been found across Eurasia. The name "mastodon" derives from Greek, μαστός "nipple" and ὀδούς "tooth", referring to their characteristic teeth.

<i>Moeritherium</i> Extinct genus of mammals

Moeritherium is an extinct genus of primitive proboscideans. These prehistoric mammals are related to the elephant and, more distantly, sea cows and hyraxes. They lived during the Eocene epoch.

<i>Stegodon</i> Genus of extinct proboscidean

Stegodon is an extinct genus of proboscidean, related to elephants. It was originally assigned to the family Elephantidae along with modern elephants but is now placed in the extinct family Stegodontidae. Like elephants, Stegodon had teeth with plate-like lophs that are different from those of more primitive proboscideans like gomphotheres and mammutids. The oldest fossils of the genus are found in Late Miocene strata in Asia, likely originating from the more archaic Stegolophodon, shortly afterwards migrating into Africa. While the genus became extinct in Africa during the Pliocene, Stegodon remained widespread in South, Southeast and East Asia until the end of the Pleistocene.

<span class="mw-page-title-main">Gomphothere</span> Extinct family of proboscidean mammals

Gomphotheres are an extinct group of proboscideans related to modern elephants. They were widespread across Afro-Eurasia and North America during the Miocene and Pliocene epochs and dispersed into South America during the Pleistocene as part of the Great American Interchange. Gomphotheres are a paraphyletic group that is ancestral to Elephantidae, which contains modern elephants, as well as Stegodontidae. While most famous forms such as Gomphotherium had long lower jaws with tusks, which is the ancestral condition for the group, some later members developed shortened (brevirostrine) lower jaws with either vestigial or no lower tusks, looking very similar to modern elephants, an example of parallel evolution, which outlasted the long-jawed gomphotheres. By the end of the Early Pleistocene, gomphotheres became extinct in Afro-Eurasia, with the last two genera, Cuvieronius ranging from southern North America to western South America, and Notiomastodon having a wide range over most of South America until the end of the Pleistocene around 12,000 years ago, when they became extinct following the arrival of humans.

Pilgrimella is an extinct early Eocene genus of anthracobunid, a group of stem perissodactyls. It was a ground dwelling grazer with massive bilophodont molars Dental remains of this animal have been found in Chorlakki, Punjab province, Pakistan, and in the Subathu Formation in North-West India.

<span class="mw-page-title-main">Mandibular second premolar</span>

The mandibular second premolar is the tooth located distally from both the mandibular first premolars of the mouth but mesial from both mandibular first molars. The function of this premolar is assist the mandibular first molar during mastication, commonly known as chewing. Mandibular second premolars have three cusps. There is one large cusp on the buccal side of the tooth. The lingual cusps are well developed and functional. Therefore, whereas the mandibular first premolar resembles a small canine, the mandibular second premolar is more alike to the first molar. There are no deciduous (baby) mandibular premolars. Instead, the teeth that precede the permanent mandibular premolars are the deciduous mandibular molars.

<i>Phiomia</i> Genus of mammals

Phiomia is an extinct genus of basal elephantiform proboscidean that lived in what is now Northern Africa during the Late Eocene to Early Oligocene some 37–30 million years ago. "Phiomia serridens" means "saw-toothed animal of Faiyum".

<i>Anancus</i> Genus of proboscideans

Anancus is an extinct genus of "tetralophodont gomphothere" native to Afro-Eurasia, that lived from the Tortonian stage of the late Miocene until its extinction during the Early Pleistocene, roughly from 8.5–2 million years ago.

<i>Daouitherium</i> Extinct genus of mammals

Daouitherium is an extinct genus of early proboscideans that lived during the early Eocene some 55 million years ago in North Africa.

<i>Numidotherium</i> Genus of mammals

Numidotherium is an extinct genus of early proboscideans, discovered in 1984, that lived during the middle Eocene of North Africa some 46 million years ago. It was about 90-100 cm tall at the shoulder and weighed about 250-300 kg.

<i>Phosphatherium</i> Extinct genus of mammals

Phosphatherium escuillei is a basal proboscidean that lived from the Late Paleocene to the early stages of the Ypresian age until the early Thanetian some 56 million years ago in North Africa. Research has suggested that Phosphatherium existed during the Eocene period.

<i>Tetralophodon</i> Extinct genus of mammals

Tetralophodon is an extinct genus of "tetralophodont gomphothere" belonging to the superfamily Elephantoidea, known from the Miocene of Afro-Eurasia.

<i>Eubelodon</i> Extinct genus of proboscid

Eubelodon is an extinct genus of gomphothere which lived in North America during the Miocene Epoch. It contains a single species: Eubelodon morrilli.

<i>Eritherium</i> Genus of mammals

Eritherium is an extinct genus of early Proboscidea found in the Ouled Abdoun basin, Morocco. It lived about 60 million years ago. It was first named by Emmanuel Gheerbrant in 2009 and the type species is Eritherium azzouzorum. Eritherium is the oldest, smallest and most primitive known elephant relative.

<i>Ocepeia</i> Extinct Afrotherian mammal

Ocepeia is an extinct genus of afrotherian mammal that lived in present-day Morocco during the middle Paleocene epoch, approximately 60 million years ago. First named and described in 2001, the type species is O. daouiensis from the Selandian stage of Morocco's Ouled Abdoun Basin. A second, larger species, O. grandis, is known from the Thanetian, a slightly younger stage in the same area. In life, the two species are estimated to have weighed about 3.5 kg (7.7 lb) and 10 kg (22 lb), respectively, and are believed to have been specialized leaf-eaters. The fossil skulls of Ocepeia are the oldest known afrotherian skulls, and the best-known of any Paleocene mammal in Africa.

Togocetus is a genus of extinct cetacean from the Lutetian of Togo, known from a fossilized skeleton discovered a few kilometers north-east of Lomé.

<span class="mw-page-title-main">Elephantiformes</span> Suborder of mammals

Elephantiformes is a suborder within the order Proboscidea that contains the elephants. Members of this group are primitively characterised by the possession of an elongated mandibular symphysis and lower tusks. The earliest known member of the group, Dagbatitherium is known from the Eocene (Lutetian) of Togo, which is only known from isolated teeth, while other elephantiforms like Phiomia and Palaeomastodon are known from the Early Oligocene onwards. Most diversity of the group is placed in the subclade Elephantimorpha, which includes modern elephants, as well as other extinct groups like mastodons and gomphotheres.

Saloumia is an extinct genus of the order Proboscidea. It is one of the oldest members of the order and lived in the middle Eocene of Senegal. It is known only from a single molar, whose pronounced bumpy chewing surface indicates it is probably closely related to Moeritherium.

References

  1. Gnandi, Kissao; Tobschall, H. (2001). "Heavy metals distribution of soils around mining sites of cadmium-rich marine sedimentary phosphorites of Kpogamé and Hahotoé (southern Togo)". Environmental Geology. 41 (5): 593–600. doi:10.1007/s002540100425. hdl: 1834/2715 . ISSN   0943-0105. S2CID   128897460.
  2. Gingerich, Philip D.; Cappetta, Henri (January 2014). "A New Archaeocete and Other Marine Mammals (Cetacea and Sirenia) from Lower Middle Eocene Phosphate Deposits of Togo". Journal of Paleontology. 88 (1): 109–129. Bibcode:2014JPal...88..109G. doi:10.1666/13-040. ISSN   0022-3360. S2CID   85915213.
  3. 1 2 3 4 5 Hautier, Lionel; Tabuce, Rodolphe; Mourlam, Mickaël J.; Kassegne, Koffi Evenyon; Amoudji, Yawovi Zikpi; Orliac, Maëva; Quillévéré, Frédéric; Charruault, Anne-Lise; Johnson, Ampah Kodjo Christophe; Guinot, Guillaume (2021-10-13). "New Middle Eocene proboscidean from Togo illuminates the early evolution of the elephantiform-like dental pattern". Proceedings of the Royal Society B: Biological Sciences. 288 (1960): 20211439. doi:10.1098/rspb.2021.1439. PMC   8511763 . PMID   34641726.
  4. Jeheskel Shoshani, W. J. Sanders und Pascal Tassy: Elephants and other Proboscideans: a summary of recent findings and new taxonomic suggestions. In: G. Cavarretta et al. (Hrsg.): The World of Elephants – International Congress. Consiglio Nazionale delle Ricerche. Rom, 2001, S. 676–679
  5. Shoshani, Jeheskel; Tassy, Pascal (2005-01-01). "Advances in proboscidean taxonomy & classification, anatomy & physiology, and ecology & behavior". Quaternary International. Studying Proboscideans: knowledge, Problems and Perspectives. Selected papers from "The world of Elephants" Congress, Rome. 126–128: 5–20. Bibcode:2005QuInt.126....5S. doi:10.1016/j.quaint.2004.04.011. ISSN   1040-6182.
  6. Gheerbrant, Emmanuel (2009-06-30). "Paleocene emergence of elephant relatives and the rapid radiation of African ungulates". Proceedings of the National Academy of Sciences. 106 (26): 10717–10721. Bibcode:2009PNAS..10610717G. doi: 10.1073/pnas.0900251106 . ISSN   0027-8424. PMC   2705600 . PMID   19549873.
  7. Gheerbrant, Emmanuel; Bouya, Baadi; Amaghzaz, Mbarek (2012-11-19). "Dental and cranial anatomy of Eritherium azzouzorum from the Paleocene of Morocco, earliest known proboscidean mammal". Palaeontographica Abteilung A. 297 (5–6): 151–183. Bibcode:2012PalAA.297..151G. doi:10.1127/pala/297/2012/151.
  8. Tabuce, Rodolphe; Sarr, Raphaël; Adnet, Sylvain; Lebrun, Renaud; Lihoreau, Fabrice; Martin, Jeremy E.; Sambou, Bernard; Thiam, Mustapha; Hautier, Lionel (May 2020). "Filling a gap in the proboscidean fossil record: a new genus from the Lutetian of Senegal". Journal of Paleontology. 94 (3): 580–588. Bibcode:2020JPal...94..580T. doi:10.1017/jpa.2019.98. ISSN   0022-3360. S2CID   213548591.