LACM 149371
Encyclopedia
LACM 149371 is an enigmatic fossil mammal
ian tooth from the Paleogene
(66 to 23 million years ago, mya) of Peru. It is from the Santa Rosa fossil site, which is of uncertain age but possibly late Eocene
(55 to 34 mya) or Oligocene
(34 to 23 mya). The tooth is poorly preserved and may have been degraded by acidic water or because it passed through a predator's digestive tract. Its largest dimension is 2.65 mm. It is triangular in shape and bears six cusps
that surround the middle of the tooth, where there are three basins (fossae). Crests connects the cusps and separate the fossae. The microscopic structure of the enamel
is poorly preserved.
LACM 149371 was described in 2004 by Francisco Goin and colleagues, who tentatively interpreted the tooth as a left last upper molar
. Although they saw similarities with South American ungulate
s, some early rodent
s, and multituberculates, they believed the tooth was most likely of a gondwanathere. Among gondwanatheres—a small and poorly known group otherwise known from the Cretaceous
through Eocene
of some of the southern continents (Gondwana
)—they thought the Cretaceous Argentinian Ferugliotherium
to be the most similar.
of Peru. The Santa Rosa fauna also contains fossils of various unique species of marsupial
s and hystricognath rodents, a possible bat
, and some notoungulates. The fauna was published in a volume of the Science Series of the Natural History Museum of Los Angeles County
in 2004, which included a paper by Francisco Goin and colleagues that described and discussed LACM 149371.
The age of the Santa Rosa fauna remains highly uncertain, as the outcrop
where the fossils were found cannot easily be placed in a known stratigraphical
unit, and the fossils are so distinct from other known fossil faunas that biostratigraphy
cannot provide a precise estimate. In a summary of the 2004 volume, Kenneth Campbell tentatively referred Santa Rosa to the Mustersan
South American Land Mammal Age
(SALMA), which he placed near the Eocene
–Oligocene
boundary, around 35 million years ago. However, Mario Vucetich and colleagues suggested in 2010 that the Santa Rosa fauna may be substantially later—perhaps as young as the Deseadan
SALMA (late Oligocene, around 25 million years ago). According to Campbell, the Santa Rosa mammals likely lived in a savanna
habitat that contained rivers.
-like tooth that largely lacks a recognizable enamel
surface and shows many small grooves and holes on the crown surface. This suggests the tooth may have been chemically degraded, perhaps by acidic water or because it passed through the digestive tract of a predator. The roots are broken off, but remaining pulp
cavities suggest the presence of four main roots, which are partially joined into two pairs. A smaller pulp cavity between those roots suggests the likely presence of a fifth root and a slight depression in the tooth may represent another root.
The crown of the tooth is triangular and contains six cusps
, connected by low crests, that surround two prominent, low-lying fossae (basins) and a third, smaller fossa. Because of the complexity of the crown, Goin and colleagues interpreted it as a molar; because of the number of roots, the arrangement of the cusps, and the shape of the tooth, as an upper molar; and because it tapers towards the end, as a last molar. One side, the longest, is flat and low compared to the others, suggesting it is the labial (outer) face. This would imply that the tooth is from the left jaw. Under this interpretation, the length of the tooth is 2.65 mm, width is 2.20 mm, height at the labial side is 1.05 mm, and height at the lingual side is 1.30 mm.
For convenience, Goin and colleagues designated the six cusps as A through F: A on the front labial corner of the tooth; B on the labial face; C on the back corner; D on the lingual (inner) face; E on the front lingual corner; and F on the front face. The large front fossa is located between cusps A, B, D, E, and F; the smaller intermediate fossa is between cusps B and D; and the much smaller back fossa is just in front of cusp C. All three are nearly round. Cusp A, the largest cusp, is triangular in shape and is separated from the smaller, rounded B by a deep valley; a low crest connects the two cusps further lingually, separating the valley from the front fossa. At its back, B connects to a long crest that reaches the back fossa and behind it the small cusp C, which has a groove on its labial side. A valley separates it from cusp D. D itself is crest-shaped and forms the lingual wall of the intermediate fossa; it is described as "very odd", and may in fact consist of two fused, triangular cusps. A crest issuing from D separates the back from the intermediate fossa, and another, larger crest separates the front from the back fossa and nearly reaches cusp B. Cusp E is triangular and separated from cusps F and D by valleys, which are bordered internally by crests connecting the cusps. F is rounded. The microstructure of the tooth enamel
is not clearly recognizable, evidently because the tooth is degraded, though structures resembling enamel prisms (bundles of hydroxyapatite crystalls) and Hunter-Schreger band
s are recognizable.
ns including monotreme
s, metatheria
ns including marsupial
s, xenarthra
ns, and some related groups. They did see some general resemblances to the upper premolar
s of the early South American ungulate
s, but the cusp arrangement is different from that of any ungulate. There are also some resemblances to the early rodent
s Ivanantonia
from Asia and Nonomys from North America, but Ivanantonia has a central groove and lacks fossae, and Nonomys has a prominent cingulum (shelf) at the edges of the tooth and also lacks the fossae of LACM 149371.
The tooth resembles multituberculates—a large group of extinct mammals with many-cusped teeth—in the shapes of the valleys and crests, but multituberculates lack fossae and usually have quadrangular teeth with two longitudinal rows of cusps separated by a central valley. In the same features, LACM 149371 resembles gondwanatheres, a small and enigmatic group of mammals from the Cretaceous
through Eocene
of the southern (Gondwana
n) continents that may be related to multituberculates. In particular, Ferugliotherium
from the late Cretaceous
of Argentina has similarly formed cusps and also has crests that connect the cusps to the center of the tooth. However, the upper molars are unknown, and the low-crowned teeth of Ferugliotherium lack deep fossae. Members of the higher-crowned gondwanathere family Sudamericidae
do have fossae. Goin and colleagues conclude that LACM 149371 most likely represents a member of the gondwanathere family Ferugliotheriidae
; if so, it would be among the youngest known gondwanatheres.
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
ian tooth from the 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...
(66 to 23 million years ago, mya) of Peru. It is from the Santa Rosa fossil site, which is of uncertain age but possibly late Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
(55 to 34 mya) or Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
(34 to 23 mya). The tooth is poorly preserved and may have been degraded by acidic water or because it passed through a predator's digestive tract. Its largest dimension is 2.65 mm. It is triangular in shape and bears six 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...
that surround the middle of the tooth, where there are three basins (fossae). Crests connects the cusps and separate the fossae. The microscopic structure of the enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
is poorly preserved.
LACM 149371 was described in 2004 by Francisco Goin and colleagues, who tentatively interpreted the tooth as a left last upper 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"....
. Although they saw similarities with South American ungulate
Ungulate
Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...
s, some early rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s, and multituberculates, they believed the tooth was most likely of a gondwanathere. Among gondwanatheres—a small and poorly known group otherwise known from the Cretaceous
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...
through Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of some 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,...
)—they thought the Cretaceous Argentinian 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...
to be the most similar.
Discovery and context
LACM 149371 was discovered in 1998 at the Santa Rosa fossil site in the Ucayali RegionUcayali Region
Ucayali is an inland region in Peru. Located in the Amazon rainforest, its name is derived from the Ucayali River. The regional capital is the city of Pucallpa.-Boundaries:...
of Peru. The Santa Rosa fauna also contains fossils of various unique species of marsupial
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
s and hystricognath rodents, a possible bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
, and some notoungulates. The fauna was published in a volume of the Science Series of the Natural History Museum of Los Angeles County
Natural History Museum of Los Angeles County
The Natural History Museum of Los Angeles County opened in Exposition Park, Los Angeles, California, USA in 1913 as the Museum of History, Science, and Art. The moving force behind it was a museum association founded in 1910. Its distinctive main building, with fitted marble walls and domed and...
in 2004, which included a paper by Francisco Goin and colleagues that described and discussed LACM 149371.
The age of the Santa Rosa fauna remains highly uncertain, as the outcrop
Outcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
where the fossils were found cannot easily be placed in a known stratigraphical
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
unit, and the fossils are so distinct from other known fossil faunas that biostratigraphy
Biostratigraphy
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...
cannot provide a precise estimate. In a summary of the 2004 volume, Kenneth Campbell tentatively referred Santa Rosa to the Mustersan
Mustersan
The Mustersan age is a period of geologic time within the Eocene epoch of the Paleogene used more specifically with South American Land Mammal Ages. It follows the Casamayoran and precedes the Divisaderan age....
South American Land Mammal Age
South American Land Mammal Age
The South American Mammal Ages establish a geologic timescale for prehistoric South American fauna beginning 64.5 Ma during the Paleogene and continuing through to the Middle Pleistocene...
(SALMA), which he placed near the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
–Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
boundary, around 35 million years ago. However, Mario Vucetich and colleagues suggested in 2010 that the Santa Rosa fauna may be substantially later—perhaps as young as the Deseadan
Deseadan
The Deseadan age is a period of geologic time within the Oligocene epoch of the Paleogene used more specifically with South American Land Mammal Ages. It follows the Tinguirirican and precedes the Colhuehuapian age....
SALMA (late Oligocene, around 25 million years ago). According to Campbell, the Santa Rosa mammals likely lived in a savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
habitat that contained rivers.
Description
LACM 149371 is a poorly preserved 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"....
-like tooth that largely lacks a recognizable enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
surface and shows many small grooves and holes on the crown surface. This suggests the tooth may have been chemically degraded, perhaps by acidic water or because it passed through the digestive tract of a predator. The roots are broken off, but remaining pulp
Pulp (tooth)
The dental pulp is the part in the center of a tooth made up of living connective tissue and cells called odontoblasts.- Anatomy :Each person can have a total of up to 52 pulp organs, 32 in the permanent and 20 in the primary teeth....
cavities suggest the presence of four main roots, which are partially joined into two pairs. A smaller pulp cavity between those roots suggests the likely presence of a fifth root and a slight depression in the tooth may represent another root.
The crown of the tooth is triangular and contains six 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...
, connected by low crests, that surround two prominent, low-lying fossae (basins) and a third, smaller fossa. Because of the complexity of the crown, Goin and colleagues interpreted it as a molar; because of the number of roots, the arrangement of the cusps, and the shape of the tooth, as an upper molar; and because it tapers towards the end, as a last molar. One side, the longest, is flat and low compared to the others, suggesting it is the labial (outer) face. This would imply that the tooth is from the left jaw. Under this interpretation, the length of the tooth is 2.65 mm, width is 2.20 mm, height at the labial side is 1.05 mm, and height at the lingual side is 1.30 mm.
For convenience, Goin and colleagues designated the six cusps as A through F: A on the front labial corner of the tooth; B on the labial face; C on the back corner; D on the lingual (inner) face; E on the front lingual corner; and F on the front face. The large front fossa is located between cusps A, B, D, E, and F; the smaller intermediate fossa is between cusps B and D; and the much smaller back fossa is just in front of cusp C. All three are nearly round. Cusp A, the largest cusp, is triangular in shape and is separated from the smaller, rounded B by a deep valley; a low crest connects the two cusps further lingually, separating the valley from the front fossa. At its back, B connects to a long crest that reaches the back fossa and behind it the small cusp C, which has a groove on its labial side. A valley separates it from cusp D. D itself is crest-shaped and forms the lingual wall of the intermediate fossa; it is described as "very odd", and may in fact consist of two fused, triangular cusps. A crest issuing from D separates the back from the intermediate fossa, and another, larger crest separates the front from the back fossa and nearly reaches cusp B. Cusp E is triangular and separated from cusps F and D by valleys, which are bordered internally by crests connecting the cusps. F is rounded. The microstructure of the tooth enamel
Tooth enamel
Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...
is not clearly recognizable, evidently because the tooth is degraded, though structures resembling enamel prisms (bundles of hydroxyapatite crystalls) and Hunter-Schreger band
Hunter-Schreger band
Hunter-Schreger bands, commonly abbreviated as HSB, are features of the enamel of the teeth in mammals, mostly placentals. In HSB, enamel prisms are arranged in layers of varying thickness at about right angles to each other...
s are recognizable.
Identity
Because of the complexity of the crown, Goin and colleagues identified the tooth as a mammal; although some non-mammalian groups, like crocodylians, may have complex teeth, none approach the level of complexity seen in LACM 149371. They could find no resemblance to australosphenidaAustralosphenida
The Australosphenida are a clade of mammals. Today, living specimens exist only in Australia and New Guinea with only five surviving species, but fossils have been found in Madagascar and Argentina...
ns including monotreme
Monotreme
Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...
s, metatheria
Metatheria
Metatheria is a grouping within the animal class Mammalia. First proposed by Thomas Henry Huxley in 1880, it is nearly synonymous with the earlier taxon Marsupialia though it is slightly wider since it also contains the nearest fossil relatives of marsupial mammals.The earliest known...
ns including marsupial
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
s, xenarthra
Xenarthra
The superorder Xenarthra is a group of placental mammals , existent today only in the Americas and represented by anteaters, tree sloths, and armadillos. The origins of the order can be traced back as far as the Paleogene in South America...
ns, and some related groups. They did see some general resemblances to the upper premolar
Premolar
The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...
s of the early South American ungulate
Ungulate
Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...
s, but the cusp arrangement is different from that of any ungulate. There are also some resemblances to the early rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s Ivanantonia
Ivanantonia
Ivanantonia is the only genus in the extinct rodent family Ivanantoniidae and is represented by a single species, Ivanantonia efremovi, from the early Eocene of Mongolia. Ivanantonia is poorly known, with only the lower dentition represented...
from Asia and Nonomys from North America, but Ivanantonia has a central groove and lacks fossae, and Nonomys has a prominent cingulum (shelf) at the edges of the tooth and also lacks the fossae of LACM 149371.
The tooth resembles multituberculates—a large group of extinct mammals with many-cusped teeth—in the shapes of the valleys and crests, but multituberculates lack fossae and usually have quadrangular teeth with two longitudinal rows of cusps separated by a central valley. In the same features, LACM 149371 resembles gondwanatheres, a small and enigmatic group of mammals from the Cretaceous
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...
through Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of the southern (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,...
n) continents that may be related to multituberculates. In particular, 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 late Cretaceous
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 has similarly formed cusps and also has crests that connect the cusps to the center of the tooth. However, the upper molars are unknown, and the low-crowned teeth of Ferugliotherium lack deep fossae. Members of the higher-crowned gondwanathere family 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...
do have fossae. Goin and colleagues conclude that LACM 149371 most likely represents a member of the gondwanathere 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...
; if so, it would be among the youngest known gondwanatheres.
Literature cited
- Campbell, K.E., Jr. 2004. The Santa Rosa local fauna: A summary. Science Series, Natural History Museum of Los Angeles County 40:155–163.
- Goin, F.J., Vieytes, E.C., Vucetich, M.G., Carlini, A.A. and Bond, M. 2004. Enigmatic mammal from the Paleogene of Perú. Science Series, Natural History Museum of Los Angeles County 40:145–153.
- Vucetich, M.G., Vieytes, E.C., Pérez, M.E. and Carloni, A.A. 2010. The rodents from La Barranca and the early evolution of caviomorphs in South America. Pp. 193–205 in Madden, R.H., Carlini, A.A., Vucetich, M.G. and Kay, R.F. (eds.). The Paleontology of Gran Barranca: Evolution and Environmental Change Through the Middle Cenozoic of Patagonia. Cambridge University Press, 458 pp. ISBN 9780521872416