Trapalcotherium
Encyclopedia
Trapalcotherium is a fossil mammal from the Cretaceous
of Argentina in the family Ferugliotheriidae
. The single species, T. matuastensis, is known from one tooth, a first lower molar
. It is from the Allen Formation
, which is probably Maastrichtian
in age, and was first described in 2009. The tooth bears two rows of cusp
s, one at the inner (lingual) side and the other at the outer (labial) side, which are connected by transverse ridges separated by deep valleys. This pattern is reminiscent of Ferugliotherium
, a gondwanathere
mammal from similarly aged deposits in Argentina, and Trapalcotherium is therefore recognized as a member of the same family Ferugliotheriidae. Ferugliotheriidae is one of two families of gondwanatheres, an enigmatic group without close relationships to any living mammals.
, southern Argentina. This locality is in the Allen Formation
, one of three formations (rock units) that have yielded Late Cretaceous
gondwanathere
fossils from Argentina (the others are the Los Alamitos
and La Colonia Formation
s). All three are probably about equally old, from the Maastrichtian
(latest Cretaceous, about 71–66 million years ago, mya) and perhaps partly the Campanian
(84–71 mya). The mammals from the Allen Formation are known from seven teeth, six of which represent four species of dryolestoids—a group of primitive mammals that dominates the Late Cretaceous mammalian faunas of Argentina. The fauna was described in a 2009 paper by Guillermo Rougier and colleagues, who named Trapalcotherium as well as several new dryolestoids. The generic name, Trapalcotherium, combines the name of the basin
where Cerro Tortuga is located, Bajo Trapalca, with the Greek therion "beast", commonly used to mean "mammal" in scientific names. The specific name, matuastensis, derives from Puesto El Matuesto, a shed
used by the paleontologists who collected the fossils from the Allen Formation.
because it has two longitudinal rows of cusps
; as a first molar because it is longer than wide; and as a left tooth because the left side (interpreted as labial, in the direction of the lips) bears more cusps than the right side (lingual, the direction of the tongue). The tooth is 2.48 mm long and 2.07 mm wide. Part of the back labial corner is missing.
The lingual row contains three cusps and the labial probably five (the broken corner renders the number uncertain). Transverse ridges, separated by deep valleys, connect the lingual and labial cusps; therefore, the cusps are not strongly separate, but rather fused. The lingual cusps are larger and separated by larger valleys than the labial ones. At the front of the tooth is a triangular structure consisting of the first lingual and the first two labial cusps. A low crest connects the first lingual to the first labial cusp and a stronger crest, separated from the first by a relatively shallow valley, connects the second lingual to the first labial cusp. Behind this structure, a second triangle is formed by two crests passing from the second lingual cusp to two cusps at the labial side (the back of the two is broken away, but its existence is presumed from the crown pattern). The front of these two crests is interrupted by a groove. The third lingual cusp is also connected to two crests, which encircle a small depression and presumably connected to one or more labial cusps, which are missing from the fossil.
—a small and enigmatic group of mammals from Cretaceous and Paleogene
of the southern continents (Gondwana
)—on the basis of the transverse ridges and triangle on its crown. It resembles Ferugliotherium
from the Los Alamitos Formation, the only previously known uncontroversial member of the family Ferugliotheriidae
, but differs in some characters: the triangle at the front is narrower in Trapalcotherium; the valley behind the front triangle is less curved; the ridges attached to the second lingual cusp form another triangle; the tooth is relatively shorter; Trapalcotherium does not have the Y-shaped valleys between cusps seen in Ferugliotherium; and the tips of the lingual cusps are more labially placed. The evolutionary affinities of gondwanatheres, which include the Ferugliotheriidae and the higher-crowned Sudamericidae
, are controversial, though a relationship with multituberculates (a large group mainly known from the northern continents of Laurasia
) has repeatedly been proposed; the identification of Trapalcotherium does not provide additional information that has a bearing on the relationships of the gondwanatheres.
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
of Argentina in the family Ferugliotheriidae
Ferugliotheriidae
Ferugliotheriidae is one of two known families in the order Gondwanatheria, an enigmatic group of extinct mammals. Gondwanatheres have been classified as a group of uncertain affinities or as members of Multituberculata, a major extinct mammalian order. The best-known representative of...
. The single species, T. matuastensis, is known from one tooth, a first lower molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
. It is from the Allen Formation
Allen Formation
The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous The Allen Formation is a geological formation in Argentina whose strata date back to the...
, which is probably Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
in age, and was first described in 2009. The tooth bears two rows of cusp
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...
s, one at the inner (lingual) side and the other at the outer (labial) side, which are connected by transverse ridges separated by deep valleys. This pattern is reminiscent of Ferugliotherium
Ferugliotherium
Ferugliotherium is a fossil mammal from the Campanian and/or Maastrichtian of Argentina in the family Ferugliotheriidae. The genus contains a single species, Ferugliotherium windhauseni, which was first described in 1986...
, a gondwanathere
Gondwanatheria
Gondwanatheria is an extinct group of mammals that lived during the Upper Cretaceous through the Eocene in the Southern Hemisphere, including Antarctica...
mammal from similarly aged deposits in Argentina, and Trapalcotherium is therefore recognized as a member of the same family Ferugliotheriidae. Ferugliotheriidae is one of two families of gondwanatheres, an enigmatic group without close relationships to any living mammals.
Discovery and context
The only known fossil of Trapalcotherium was found at Cerro Tortuga in Río Negro ProvinceRío Negro Province
Río Negro is a province of Argentina, located at the northern edge of Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean.Its capital is Viedma...
, southern Argentina. This locality is in the Allen Formation
Allen Formation
The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous The Allen Formation is a geological formation in Argentina whose strata date back to the...
, one of three formations (rock units) that have yielded Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
gondwanathere
Gondwanatheria
Gondwanatheria is an extinct group of mammals that lived during the Upper Cretaceous through the Eocene in the Southern Hemisphere, including Antarctica...
fossils from Argentina (the others are the Los Alamitos
Los Alamitos Formation
The Los Alamitos Formation is a geological formation in Rio Negro, Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Dinosaurs:-Mammaliaforms:-References:...
and La Colonia Formation
La Colonia Formation
The La Colonia Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation....
s). All three are probably about equally old, from the Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
(latest Cretaceous, about 71–66 million years ago, mya) and perhaps partly the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
(84–71 mya). The mammals from the Allen Formation are known from seven teeth, six of which represent four species of dryolestoids—a group of primitive mammals that dominates the Late Cretaceous mammalian faunas of Argentina. The fauna was described in a 2009 paper by Guillermo Rougier and colleagues, who named Trapalcotherium as well as several new dryolestoids. The generic name, Trapalcotherium, combines the name of the basin
Sedimentary basin
The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification...
where Cerro Tortuga is located, Bajo Trapalca, with the Greek therion "beast", commonly used to mean "mammal" in scientific names. The specific name, matuastensis, derives from Puesto El Matuesto, a shed
Shed
A shed is typically a simple, single-storey structure in a back garden or on an allotment that is used for storage, hobbies, or as a workshop....
used by the paleontologists who collected the fossils from the Allen Formation.
Description
The single tooth of Trapalcotherium is identified as a lower molarMolar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
because it has two longitudinal rows of cusps
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...
; as a first molar because it is longer than wide; and as a left tooth because the left side (interpreted as labial, in the direction of the lips) bears more cusps than the right side (lingual, the direction of the tongue). The tooth is 2.48 mm long and 2.07 mm wide. Part of the back labial corner is missing.
The lingual row contains three cusps and the labial probably five (the broken corner renders the number uncertain). Transverse ridges, separated by deep valleys, connect the lingual and labial cusps; therefore, the cusps are not strongly separate, but rather fused. The lingual cusps are larger and separated by larger valleys than the labial ones. At the front of the tooth is a triangular structure consisting of the first lingual and the first two labial cusps. A low crest connects the first lingual to the first labial cusp and a stronger crest, separated from the first by a relatively shallow valley, connects the second lingual to the first labial cusp. Behind this structure, a second triangle is formed by two crests passing from the second lingual cusp to two cusps at the labial side (the back of the two is broken away, but its existence is presumed from the crown pattern). The front of these two crests is interrupted by a groove. The third lingual cusp is also connected to two crests, which encircle a small depression and presumably connected to one or more labial cusps, which are missing from the fossil.
Relationships
Trapalcotherium is identified as a member of GondwanatheriaGondwanatheria
Gondwanatheria is an extinct group of mammals that lived during the Upper Cretaceous through the Eocene in the Southern Hemisphere, including Antarctica...
—a small and enigmatic group of mammals from Cretaceous and Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
of the southern continents (Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
)—on the basis of the transverse ridges and triangle on its crown. It resembles Ferugliotherium
Ferugliotherium
Ferugliotherium is a fossil mammal from the Campanian and/or Maastrichtian of Argentina in the family Ferugliotheriidae. The genus contains a single species, Ferugliotherium windhauseni, which was first described in 1986...
from the Los Alamitos Formation, the only previously known uncontroversial member of the family Ferugliotheriidae
Ferugliotheriidae
Ferugliotheriidae is one of two known families in the order Gondwanatheria, an enigmatic group of extinct mammals. Gondwanatheres have been classified as a group of uncertain affinities or as members of Multituberculata, a major extinct mammalian order. The best-known representative of...
, but differs in some characters: the triangle at the front is narrower in Trapalcotherium; the valley behind the front triangle is less curved; the ridges attached to the second lingual cusp form another triangle; the tooth is relatively shorter; Trapalcotherium does not have the Y-shaped valleys between cusps seen in Ferugliotherium; and the tips of the lingual cusps are more labially placed. The evolutionary affinities of gondwanatheres, which include the Ferugliotheriidae and the higher-crowned Sudamericidae
Sudamericidae
Sudamericidae is a family of gondwanathere mammals that lived during the late Cretaceous to Eocene. Its members include Lavanify from the Cretaceous of Madagascar, Bharattherium from the Cretaceous of India, Gondwanatherium from the Cretaceous of Argentina, Sudamerica from the Paleocene of...
, are controversial, though a relationship with multituberculates (a large group mainly known from the northern continents of Laurasia
Laurasia
In paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...
) has repeatedly been proposed; the identification of Trapalcotherium does not provide additional information that has a bearing on the relationships of the gondwanatheres.
Literature cited
- Rougier, G.W., Chornogubsky, L., Casadio, S., Paéz Arango, N. and Giallombardo, A. 2009. Mammals from the Allen Formation, Late Cretaceous, Argentina (subscription required). Cretaceous Research 30:223–238.