Tremacebus

Tremacebus
Skull of Tremacebus , holotype
Temporal occurrence
Lower Miocene
20.4 to 17.4 million years
Locations
South America ( Patagonia )
Systematics
Primates (Primates) Dry- nosed primates (Haplorrhini) Monkey (anthropoidea) New World Monkey (Platyrrhini) incertae sedis Tremacebus
Scientific name
Tremacebus
Hershkovitz , 1974

Tremacebus is an extinct genus of primates that has beenpassed downfrom the Argentine province of Chubut via a single but damaged skull. The age of the find is estimated at around 20 to 17 million years, which means itbelongsto the Lower Miocene . It belongs to a small representative of the New World monkeys , roughly the size of today's night monkeys or the jumping monkeys . The most noticeable feature on the skull is the enlarged eye windows . For a long time this led to the assumption that Tremacebus, comparable to the night monkeys, was mainly active during the dark time of day. However, more recent studies contradict this view. The skull was found in 1932 and presented a year later. For a long time it was considered to belong to Homunculus, another form of primate that was also extinct. Onlynew anatomical examinations from 1974 led to the establishment of the genus Tremacebus .

features

Tremacebus was a small to medium-sized representative of the New World monkeys with an assumed weight of around 1.8 kg. It has largely come down to us about a damaged skull with missing parts of the rostrum , the zygomatic arches and parts of the occiput. Its length when complete was approximately 6.1 to 6.3 cm, the width at the skull was about 5.1 cm. At eye level it reached a width of about 3.8 cm, behind it it was clearly drawn in and was only 2.8 cm wide here. Despite some missing parts of the snout region, such as the middle jawbone , it was probably formed quite broad, which can be deduced from the clear distance between the tooth sockets of the canines . It may also protrude prominently and was therefore prognathic . A striking feature of Tremacebus was the enlarged orbit , they were 1.6 cm wide and 1.5 cm high. As a result, they did not reach the dimensions of today's eastern gray-throated night monkeys ( Aotus trivirgatus ), whose eye windows are about 1.95 cm wide with the same skull length, but were larger than the red-bellied jumper ( Callicebus moloch ) with 1.36 cm with the corresponding Skull size. The orbits of Homunculus and Dolichocebus had similar dimensions to the latter . The convergence of the eyes to one another was relatively small and comparable to that of today's marmosets , in which the eyes are at an angle of 58 to 63 ° to one another. Other New World monkeys have a larger angle (66 to 75 °), as do Old World monkeys (70 to 83 °). Since numerous early primates are characterized by a smaller corner of the eye, the feature in Tremacebus can be interpreted as original, while in the marmosets it probably emerged secondary. According to original descriptions, there were larger fissures in the eye socket next to the foramen opticum , but these openings are probably due to damage after the death of the animal. This may also affect the supposedly large opening in the back of the eye. The infraorbital foramen lay above the second and third premolars and was about half a millimeter in size. At the pterion (a region to the side of the eyes in the human skull) the parietal bone met the cheekbone , which corresponds to the anatomical conditions in New World monkeys. In the case of Homunculus, however , this feature was more polymorphic, since in some skulls the suture of the sphenoid and frontal bone ran here. The latter is more typical of the Old World monkeys . Similar to Dolichocebus, there was a slight temporal line on the parietal bone, but there was no parietal ridge . In agreement with Dolichocebus, there was a small postglenoidal process at the base of the skull , which in turn was larger in Homunculus . The foramen postglenoideum behind it was also small and with a diameter of 0.7 mm it was only a little more than a third of the width of Dolichocebus and Homunculus . The occipital scale of the occiput was at a more obtuse angle to the eye-ear level as in most New World monkeys, but in contrast to the conspicuously acute angle in the squirrel monkeys .

The Tremacebus dentition is poorly preserved, the molars are largely preserved , but with damage on the cheek side, as well as the alveoli of the premolars and the canine. As with all New World monkeys, the rear dentition consisted of three pre-grinding and three molar teeth on each side of the jaw. The second, i.e. the foremost premolar, had a root identical to most of the early and numerous recent New World monkeys, with the exception of the night monkeys, the howler monkeys, and some jumper monkeys . The other two premolars each had two roots. On the chewing surface of the two anterior molars, the main cusps on the tongue side, the protoconus and the hypococus, were almost the same size. A well-defined entoflexus (an enamel fold ) ran between them . Near the protoconus, the periconus was a smaller side hump that was also present in other early New World monkeys such as Branisella . Also on the tongue side of the molars bulged out a pronounced and elongated cingulum (a low enamel bulge). The rearmost molar was only about half the size of the two anterior ones. The length of the molar row was 0.9 cm, that of the pre-molar row 0.7 cm. The entire row of teeth preserved from the canine to the last molar extended over 1.8 cm in length.

Fossil finds

The only known skull of Tremacebus so far comes from a site about 12 km southwest of Cerro Sacanana in the central-northern part of the Argentine province of Chubut . It was found in 1932 by a local shepherd who passed it on to a rancher along with other fossil remains . The following year, the skull was presented by Carlos Rusconi and for a long time remained the only relic of Cerro Sacanana described in detail. It was also Rusconi who provided one of the few geological descriptions of the site in 1935 , but he had never visited the region. In the following years it did not remain in the focus of the scientists. It was not until the early 1980s that American scientists revisited the site and discovered a large number of fossil remains (around 500 objects). Among them was a left lower jaw remnant of a New World monkey with the preserved last premolar and the first molar as well as the alveoli of the two preceding premolars and the canine (copy number MACN-CH 354). In size and shape it corresponds to the skull of Tremacebus and is therefore provisionally assigned to the genus, but sometimes also associated with Soriacebus . The location at Cerro Sacanana is on the southern edge of the Meseta de Somun Cura , a larger volcanic field . The small outcrops are distributed over an area of ​​around 3  hectares , the fossils found there are mostly enclosed in concretions and stored exposed on the surface. The fauna material, which has not been studied so far, consists of primate remains and various rodents . It is summarized as Sacanana fauna and classified due to its composition in the Lower Miocene around 21 to 17.5 million years ago (locally stratigraphically called Colhuehuapium ).

Paleobiology

Today's New World monkeys are largely diurnal. An exception are the night monkeys ( Aotus ), which are fully or partially nocturnal. A comparable nocturnal way of life among the dry-nosed monkeys is only shown by the tarsier (Tarsiidae). Anatomical evidence for this can be found in the extremely large eye sockets, which clearly surpass those of the same size and nocturnal wet-nosed monkeys . In contrast to the wet-nosed monkeys, the dry-nosed monkeys lack the tapetum lucidum , a reflective layer behind the retina that increases the eyesight of many nocturnal mammals during the dark time of day. The adaptations of the dry-nosed monkeys to a nocturnal life can therefore be traced back to a secondary development, which also explains the overly extended eye windows. Tremacebus has an enlarged orbit, which is why a nocturnal lifestyle was assumed early on. However, it does not reach the proportions of the night monkey, rather it mediates between the daytime and nocturnal New World monkeys. As a further adaptation to a nightlife, the olfactory bulb is enlarged in the night monkeys . This forms part of the olfactory organ, with a strong expansion of the olfactory bulb being accompanied by a more pronounced sense of smell . In nocturnal primates, smell perception usually dominates over a precise sense of sight . The olfactory bulb passes the olfactory fossa , which is located between the eyes and whose size can be used as an indicator of the dimensions of the olfactory bulb in extinct monkeys. In Tremacebus , the olfactory fossa shows itself to be comparatively small both in relative and absolute terms in relation to brain size. Their size is in proportion to that of the sakia monkey or the squirrel monkey . According to this, a more diurnal lifestyle would be assumed for Tremacebus , possibly also a cathemeral one .

On the basis of the broad molars and the little developed temporal lines on the parietal bone, Tremacebus concludes that the main diet is a rather soft vegetable diet, possibly similar to the jugular monkeys with their predominantly fruit- based diet.

Systematics

Internal systematics of the New World monkeys according to the Long Lineage Hypothesis according to Silvestro et al. 2019  Platyrrhini    Perupithecus (†)      Scalatavus (†)      Lagonimico (†)      Canaanimico (†)       Pitheciidae    Homunculus (†)      Carlocebus (†)      Callicebinae      Xenotrichini (†)      Mazzonicebus (†)      Soriacebus (†)      Pitheciinae      Branisella (†)       Atelidae    Chilecebus (†)      Atelinae      Stirtonia (†)      Alouattinae       Cebidae    Panamacebus (†)      Dolichocebus (†)      Saimiriinae      Kilikaike (†)      Cebinae      Callitrichidae   Aotidae   Tremace bus (†)      Aotinae shortened; In addition to the recent groups, only the fossil forms from the Eocene to the Lower Miocene are shown

Internal systematics of the New World monkeys according to the Stem Platyrrhine Hypothesis according to Marivaux et al. 2016  Platyrrhini    Perupithecus (†)      Branisella (†)       "Homunculidae"    Carlocebus (†)      Homunculus (†; including Kilikaike )      Mazzonicebus (†)      Canaanimico (†)      Soriacebus (†)      Dolichocebus (†)      Tremace bus (†)      Chilecebus (†)      Xenotrichini (†)       Pitheciidae    Callicebinae      Pitheciinae       Atelidae    Atelinae       Stirtonia (†)      Alouattinae      Aotidae   Cebidae   Cebinae      Saimiriinae + Panamacebus (†)   Callitrichidae    Lagonimico (†)      Saguinini + Callitrichini shortened; In addition to the recent groups, only the fossil forms from the Eocene to the Lower Miocene are shown

Tremacebus is a genus from the order of the primates (Primates). It is placed within the primates group of the New World monkeys (Platyrrhini). The New World monkeys are mostly arboreal monkeys from the tropical and subtropical regions of South and Central America . They include several families , the sakia monkeys ( Pitheciidae), the spotted monkeys ( Atelidae), the capuchins (Cebidae) and the marmosets (Callitrichidae). As a rule, the sakia monkeys are a sister group to the other groups of the New World monkeys, which can also be proven by molecular genetics . The earliest appearance of the New World monkeys dates back to the transition from the Eocene to the Oligocene around 35 million years ago and is associated with Perupithecus . The few teeth found so far came from the Peruvian area of ​​the Amazon basin .

The systematic position of Tremacebus is currently under discussion. The first person to describe the genus, Philip Hershkovitz , saw the fossil form in 1974 classified within the Capuchin-like family, where it should belong to an independent subfamily he had newly established, the Tremacebinae. According to other authors, Tremacebus is closer to the night monkeys and together with them is assigned to the subfamily of the Aotinae or - under certain circumstances together with the night monkeys and sometimes also with the jumper monkeys - referred to the subfamily of the Homunculinae (sometimes also with the rank of a tribe ). Depending on the preferred system, both subfamilies are sometimes considered to be members of the Sakia monkeys. In addition to the attempts to connect Tremacebus with individual lines of the New World monkeys that still exist today, various other scientists assign the early representatives of the Lower and Middle Miocene to a basal radiation phase of the Platyrrhini. They are then sometimes viewed as an independent family of the Homunculidae. (The name was introduced by Florentino Ameghino in 1894 and refers to Homunculus .) However, since these original forms do not necessarily form a self-contained, i.e. monophyletic group, they are sometimes given the status incertae sedis .

Mainly responsible for the problematic assignment of Tremacebus (and other early New World monkeys) are two competing hypotheses about the phylogeny of the New World monkeys that are currently controversial. According to the Long Lineage Hypothesis (or Morphological Stasis Hypothesis ), the extinct forms of the Lower and Middle Miocene represent the original representatives of the crown group of the New World monkeys. In contrast, the Stem Platyrrhine Hypothesis (or Successive Radiations Hypothesis ) classifies these primitive forms as part of a basal diversification group . The advocates of the respective view cite various molecular genetic studies on recent New World monkeys to support this, but these are inconclusive because they use different calibration models. The proponents of the Morphological Stasis Hypothesis put today's New World monkeys at 29 to 31 million years ago, whereas the Stem Platyrrhine Hypothesis started at around 20 million years ago, which is much younger.

The only skull of Tremacebus to date , found at Cerro Sacanana in the Argentine province of Chubut , was characterized in a short essay by Carlos Rusconi in 1933 . Due to the size of the find, he saw the best matches with Homunculus , a fossil form of the New World monkey from the Santa Cruz Formation in Patagonia , which was named by Florentino Ameghino at the end of the 19th century . Therefore Rusconi had the skull of the new species Homunculus harringtoni to and thanked the epithet at Thomas Harrington , a rancher , who had previously passed the fossil together with other finds in him. Two years after the first description, Rusconi published a more comprehensive description of the fossil skull. Again, some four decades later saw Philip Hershkovitz important in the structure of the orbit differences Homunculus and established with Tremacebus a new generic name for Rusconis Art. In his first description of Tremacebus in 1974 he presented the Fund, as holotype both for the species the species T. harringtoni (collection number 661 of the Museo de Fundación Miguel Lillo, Tucumán, Argentina) also functions appropriately under the new aspects. He derived the name from the large opening in the back of the eye. The skull had been extensively restored between Rusconi's publications and Hershkovitz's new appraisal, and missing parts had been added interpretively. Hershkovitz was only able to partially reverse this during his anatomical studies. Only CT scans at the beginning of the 2000s uncovered the actual fossil again and thus enabled more in-depth analyzes.

literature

• Philip Hershkovitz: A new genus of Late Oligocene monkey (Cebidae, Platyrrhini) with notes on postorbital closure and platyrrhine evolution. Folia Primatologica 21, 1974, pp. 1-35
• Richard F. Kay, Victoria M. Campbell, James B. Rossie, Matthew W. Colbert and Tim B. Rowe: Olfactory Fossa of Tremacebus harringtoni (Platyrrhini, Early Miocene, Sacanana, Argentina): Implications for Activity Pattern. The Anatomical Record 281 A, 2004, pp. 1157-1172

Individual evidence

1. ^ ^{A b} Daniele Silvestro, Marcelo F. Tejedor, Martha L. Serrano-Serrano, Oriane Loiseau, Victor Rossier, Jonathan Rolland, Alexander Zizka, Sebastian Höhna, Alexandre Antonelli and Nicolas Salamin: Early Arrival and Climatically-Linked Geographic Expansion of New World Monkeys from Tiny African Ancestors. Systematic Biology 68 (1), 2019, pp. 78-92
2. ↑ ^{a b c d e f g} Philip Hershkovitz: A new genus of Late Oligocene monkey (Cebidae, Platyrrhini) with notes on postorbital closure and platyrrhine evolution. Folia Primatologica 21, 1974, pp. 1-35
3. ↑ ^{a b c d e f} Richard F. Kay, JG Fleagle, TRT Mitchell, Matthew Colbert, Tom Bown and Dennis W. Powers: The anatomy of Dolichocebus gaimanensis, a stem platyrrhine monkey from Argentina. Journal of Human Evolution 54, 2008, pp. 323-382
4. ^ ^{A b} Jonathan MG Perry, Richard F. Kay, Sergio F. Vizcaíno and M. Susana Bargo: Oldest known cranium of a juvenile New World monkey (Early Miocene, Patagonia, Argentina): Implications for the taxonomy and the molar eruption pattern of early platyrrhines. Journal of Human Evolution 74, 2014, pp. 67-81
5. ↑ Ethan L. Fulwood, Doug M. Boyer and Richard F. Kay: Stem members of Platyrrhini are distinct from catarrhines in at least one derived cranial feature. Journal of Human Evolution 100, 2016, pp. 16-24
6. ^ ^{A b} Kenneth D. Rose and John G. Fleagle: The third radiation - Higher primates. In: Russell L. Ciochon and John G. Fleagle (Eds.): Primate Evolution and Human Origins. Transactions publishers, 1985, pp. 124-132
7. ^ ^{A b c} John G. Fleagle and Thomas M. Bown: New primate fossils from Late Oligocene (Colhuehuapian) localities of Chubut province, Argentina. Folia Primatologia 41, 1983, pp. 240-266
8. ↑ ^{a b} Richard F. Kay: An new primate from the Early Miocene of Gran Barranca, Chubut province, Argentina: paleoecological implications. In: Richard H. Madden, Alfredo A. Carlini, Maria Guiomar Vucetich and Richard F. Kay (Eds.): The Paleontology of Gran Barranca: Evolution and Environmental Change. Cambridge University Press, 2010, pp. 220-239
9. ^ John G. Fleagle: New fossil platyrrhines from the Pinturas Formation, southern Argentina. Journal of Human Evolution 19, 1990, pp. 61-85
10. ↑ Maria Guiomar Vucetich, AG Kramarz and AM Candela: Colhuehuapian rodents from Gran Barranca and othe Patagonian localities: the state of the art. In: Richard H. Madden, Alfredo A. Carlini, Maria Guiomar Vucetich and Richard F. Kay (Eds.): The Paleontology of Gran Barranca: Evolution and Environmental Change. Cambridge University Press, 2010, pp. 206-219
11. ↑ ^{a b c} Richard F. Kay, Victoria M. Campbell, James B. Rossie, Matthew W. Colbert and Tim B. Rowe: Olfactory Fossa of Tremacebus harringtoni (Platyrrhini, Early Miocene, Sacanana, Argentina): Implications for Activity Pattern. The Anatomical Record 281 A, 2004, pp. 1157-1172
12. ↑ Ann Gibbons: Seeing what an extinct monkey saw. Science 304, 2004, p. 819
13. ↑ ^{a b c} Laurent Marivaux, Sylvain Adnet, Ali J. Altamirano-Sierra, Myriam Boivin, François Pujos, Anusha Ramdarshan, Rodolfo Salas-Gismondi, Julia V. Tejada-Lara and Pierre-Olivier Antoine: Neotropics provide insights into the emergence of New World monkeys: New dental evidence from the late Oligocene of Peruvian Amazonia. Journal of Human Evolution 97, 2016, pp. 159-175
14. ↑ Horacio Schneider and Iracilda Sampaio: The systematics and evolution of New World primates - A review. Molecular Phylogenetics and Evolution 82, 2015, pp. 348-357, doi: 10.1016 / j.ympev.2013.10.017
15. ^ F. Dumas and S. Mazzoleni: Neotropical primate evolution and phylogenetic reconstruction using chromosomal data. Italian Journal of Zoology 84 (1), 2017, pp. 1-18, doi: 10.1080 / 11250003.2016.1260655
16. ↑ Xiaoping Wang, Burton K. Lim, Nelson Ting, Jingyang Hu, Yunpeng Liang, Christian Roos and Li Yu: Reconstructing the phylogeny of new world monkeys (platyrrhini): evidence from multiple non-coding loci. Current Zoology, 2018, pp. 1-10, doi: 10.1093 / cz / zoy072
17. ↑ Mariano Bond, Marcelo F. Tejedor, Kenneth E. Campbell Jr., Laura Chornogubsky, Nelson Novo and Francisco Goin: Eocene primates of South America and the African origins of New World monkeys. Nature 520 (7548), 2015, pp. 538-541
18. ^ Alfred L. Rosenberger, Marcelo F. Tejedor, Siobhán B. Cooke and Stephen Pekar: Platyrrhine ecophylogenetics in space and time. In: PA Garber, A. Estrada, JC Bicca-Marques, EW Heymann EW and KB Strier (eds.): South American primates: comparative perspectives in the study of behavior, ecology and conservation. New York, Springer, 2009, pp. 69-113
19. ^ ^{A b} Alfred L. Rosenberger: Platyrrhines, PAUP, parallelism, and the Long Lineage Hypothesis: A reply to Kay et al. (2008). Journal of Human Evolution 59, 2010, pp. 214-217
20. ^ Alfred L. Rosenberger: Evolutionary Morphology, Platyrrhine Evolution, and Systematics. The Anatomical Record 294, 2011, pp. 1955-1974
21. ↑ Marcelo F. Tejedor: Sistemática, evolución y paleobiogeografía de los primates Platyrrhini. Revista del Museo de La Plata Sección Zoología 20 (176), 2013, pp. 20-39
22. ↑ Florentino Ameghino: Enumération synoptique des espèces de mammifères fossiles des formations éocènes de Patagonia. Buenos Aires, 1894, pp. 1–196 (pp. 9–11 and 102) ( digitized version )
23. ^ Richard F. Kay: Biogeography in deep time - What do phylogenetics, geology, and paleoclimate tell us about early platyrrhine evolution? Molecular Phylogenetics and Evolution 82, 2015, pp. 358-374
24. ↑ Jessica W. Lynch Alfaro, Liliana Cortés-Ortiz, Anthony Di Fiore and Jean P. Boubli: Comparative biogeography of Neotropical primates. Molecular Phylogenetics and Evolution 82, 2015, pp. 518-529
25. ^ S. Ivan Perez, Marcelo F. Tejedor, Nelson M. Novo and Leandro Aristide: Divergence Times and the Evolutionary Radiation of New World Monkeys (Platyrrhini, Primates): An Analysis of Fossil and Molecular Data. PLoS ONE 8 (6), 2013, p. E68029, doi: 10.1371 / journal.pone.0068029
26. ↑ Jason A. Hodgson, Kirstin N. Sterner, Luke J. Matthews, Andrew S. Burrell, Rachana A. Jani, Ryan L. Raaum, Caro-Beth Stewart, and Todd R. Disotell: Successive radiations, not stasis, in the South American primate fauna. PNAS 106 (14), 2009, pp. 5534-5539
27. ↑ Florentino Ameghino: Nuevos restos de mamiferos fosiles decubiertos par Carlos Ameghino en el eoceno inferior de la Patagonia austral. - Especies nuevas, adiciones y correcciones. Revista Argentina de Historia Natural 1, 1891, pp. 289–328 ( digitized version )
28. ↑ Florentino Ameghino: Los monos fósiles del eoceno de la república Argentina. Revista Argentina de Historia Natural 1, 1891, pp. 383–397 ( digitized version )
29. ↑ Carlos Rusconi: Nuevos restos de monos fósiles del TERCIARIO antiguo de la Patagonia. Anales de la Sociedad Científica Argentina 116, 1933, pp. 286–289 ( digitized version )