Plesiorycteropus
Encyclopedia
Plesiorycteropus, also known as the bibymalagasy or Malagasy aardvark, is a recently extinct eutheria
n mammalian genus
from Madagascar
. Upon its description in 1895, it was classified with the aardvark
, but recent studies have found little evidence to link it to aardvarks or any other order
of mammals. Therefore, it is now placed in its own order, Bibymalagasia, which may be part of Afrotheria
. Two species are currently recognized, the larger P. madagascariensis and the smaller P. germainepetterae. They probably overlapped in distribution, as subfossil
remains of both species have been found in the same site.
Knowledge of the skeletal anatomy is limited, as only limb and partial pelvis and skull bones have been recovered to date. Plesiorycteropus was probably a digging animal that fed on insects such as termite
s and ant
s. It also shows adaptations for climbing and sitting. Estimates of its mass range from 6 to 18 kg (13.2 to 39.7 lb). When and why it became extinct remains unknown. One bone has been radiocarbon dated
to 200 BCE; forest destruction by humans may have contributed to its extinction.
first described Plesiorycteropus madagascariensis in 1895 on the basis of a partial skull found at the cave of Belo
. His description was vague even for 19th-century standards, but he placed the animal close to the aardvark
(Orycteropus). The generic name combines Ancient Greek
plesio- "near" with Orycteropus, the genus of the aardvark, and the specific name refers to Madagascar. Charles Lamberton, who had access to a larger sample for his 1946 review of the genus, noted substantial variation, but did not attempt to differentiate multiple species. In 1994, Ross MacPhee again reviewed Plesiorycteropus and was able to separate two species, the larger P. madagascariensis and a new, smaller species that he named Plesiorycteropus germainepetterae after scientist Germaine Petter. The two species differ in a number of morphological characters in addition to size.
Remains of Plesiorycteropus have been misidentified as rodents and primates. Charles Immanuel Forsyth Major
described Myoryctes rapeto in 1908 as a "giant subfossil rat" on the basis of two innominate bones (pelvic bones). The generic name was replaced by Majoria in 1915, because Myoryctes was preoccupied by the name of a nematode
worm. However, according to MacPhee, innominates of Majoria are identical to those assigned to Plesiorycteropus. Guillaume Grandidier
assigned a well-preserved femur
(upper leg bone) to a gigantic relative of the living votsovotsa (Hypogeomys antimena), a large rodent, which he described as Hypogeomys boulei. Lamberton identified this femur as Plesiorycteropus and MacPhee concurred. Remains of both Majoria rapeto and Hypogeomys boulei fall at the upper end of the size range of the genus, indicating that they are referable to P. madagascariensis. Another Plesiorycteropus innominate was mistakenly assigned to Daubentonia robusta, the extinct giant aye-aye, and other material has been misidentified as of a dwarf lemur
(Cheirogaleus).
s, armadillo
s, and anteater
s. He believed it was most likely a primitive, isolated member of "Edentata", a group in which he included aardvarks, pangolins, and Xenarthra
(sloths, armadillos, and anteaters). He rejected some alternatives, such as a close affinity to aardvarks or the possibility that the material assigned to Plesiorycteropus did not in fact represent a single animal. Bryan Patterson, who revised tubulidentates (the order of which the aardvark is the only living representative) in the 1970s, accepted Plesiorycteropus as a member of the group, dismissing many similarities with pangolins and other animals as convergent
. However, he placed it as the only member of its own subfamily Plesiorycteropodinae in view of its differences from other tubulidentates (subfamily Orycteropodinae), and hypothesized that it arrived on Madagascar in the Eocene
, at the same time as the lemur
s. Johannes Thewissen, who critiqued some aspects of Patterson's classification in 1985, also accepted Plesiorycteropus as a tubulidentate without comment.
Reviewing Patterson's and Thewissen's contributions in 1994, Ross MacPhee found little support for the classification of Plesiorycteropus as a tubulidentate in their data. MacPhee used a cladistic
analysis of eutherians to ascertain the relationships of the genus, but found that while different analytic variants supported different affinities—with aardvarks, hyrax
es, ungulate
s (hooved mammals), and even lipotyphlans (shrews, moles, hedgehogs, and allies)—there was no compelling evidence linking it to any other eutherian group. Therefore, he erected a separate order for Plesiorycteropus, named Bibymalagasia, arguing that it would be unacceptable to leave a Recent eutherian unassigned to any order and that discovery of more material, or further analysis, was unlikely to demonstrate close affinities of Plesiorycteropus with any other order. He considered it possible but unlikely that a few fossil taxa, such as Palaeorycteropus and Leptomanis from the Paleogene
of France, would eventually be found to be bibymalagasians. Various analyses published by Robert Asher and colleagues in 2003, 2005, and 2007, based on morphology combined with DNA sequence
data in some analyses, produced different estimates of the relationships of Plesiorycteropus, some placing it within Afrotheria
close to aardvarks or Afrosoricida
, but others supporting a relationship with the hedgehog Erinaceus
. A 2004 morphological study by Inés Horovitz, focusing on extinct South American ungulates (such as Notoungulata
and Litopterna
), placed Plesiorycteropus among tubulidentates and closer to the extinct aardvark relative Myorycteropus than to Orycteropus.
for Plesiorycteropus, but MacPhee considered it inappropriate because the animal may not be related to aardvarks. Instead, he proposed "bibymalagasy" as a common name, a manufactured Malagasy
word meaning "Malagasy animal".
bones, comparable to coverage of some of the poorly known subfossil lemur
s, such as Daubentonia robusta. The material includes several skulls, all of which are missing the facial bones, complete long bones such as the femur and humerus
(upper arm bone), and other bones, but some elements are still unknown, including most of the skeleton of the hand and foot. There is little reason to assume it was similar in general form to the aardvark. No teeth or jaws referable to Plesiorycteropus have been found, and it is generally assumed that the animal was toothless.
Based on the area of a femur cross-section, MacPhee calculated estimates of body mass. The lowest estimate, based on comparative data from armadillos and pangolins, was 6 kilograms (13.2 lb) for the smallest femur he had (referable to P. germainepetterae) and the highest estimate, based on comparative data from caviomorph rodents, was 18 kilograms (39.7 lb) for the largest available femur (P. madagascariensis); estimates from primates fell between those extremes. MacPhee favored the lower estimates, because those were based on armadillos, which have femora similar to those of Plesiorycteropus. On the other hand, the caviomorph model produced a better estimate of brain size in Plesiorycteropus.
averages 35.4 millimetres (1.4 in) in P. madagascariensis and is 29.4 millimetres (1.2 in) in P. germainepetterae.
The robust nasal bone
s, preserved in a single specimen, are widest at the front, a feature unusual among placentals that is also seen in armadillos, and are also unusually flat. The ethmoid labyrinth, in the nasal cavity
, was large, suggesting that Plesiorycteropus had a good sense of smell. A much larger part of the nasal septum
, which separates the left and right nasal cavities, is ossified than usual in other mammals; MacPhee could find a similar condition only in sloths, which have a very short nose. The lacrimal bone
is relatively large. At it is a single lacrimal canal, which opens near the suture
between the frontal and lacrimal bones, like in lipotyphlans. There is a small tubercle (absent in aardvarks) near this opening. The orbital cavity, which houses the eyes, is relatively short, similar to the situation in pangolins and armadillos. A distinct tubercle is present on the suture between the frontal and parietal bone
s in P. germainepetterae, but not P. madagascariensis. P. madagascariensis has a more expansive braincase and a less pronounced narrowing between the orbits. The foramen rotundum
, an opening in the bone of the orbit, is present. The optic canal, which houses the nerves leading to the eyes, is narrow, suggesting that the eyes were small. As in pangolins and xenarthrans, little of the squamosal bone can be seen from above. The temporal line
s on the braincase, which anchor muscles, are located lower in P. germainepetterae. Like in aardvarks, the parietals are relatively large. An interparietal bone is present. Unlike in anteaters and pangolins, the occiput
(the back of the skull) is flat and vertical. Plesiorycteropus lacks notches above the foramen magnum (the opening that connects the brain to the spinal cord
), which are present in aardvarks. The nuchal crest, a projection on the occiput, is straight in P. madagascariensis, but in P. germainepetterae it is interrupted in the middle, similar to the situation in armadillos and hyraxes.
In their descriptions of Plesiorycteropus, Lamberton and Patterson posited different interpretations of the location of the mandibular fossa
, where the mandible
(lower jaw) articulates with the cranium. MacPhee found problems with either interpretation and suggested that the true mandibular fossa was part of the area Lamberton identified as such, at the side of the braincase. The fossa is small and low, suggesting that the animal was not capable of powerful biting. At the back of this fossa is a pseudoglenoid proces, which is more prominent in P. germainepetterae. In P. germainepetterae but not P. madagascariensis, a small opening, perhaps the vascular foramen, is present next to the foramen ovale
. The petrosal bone forms a relatively large portion of the roof of the tympanic cavity
, which houses the middle ear; parts of the petrosal are more developed in P. madagascariensis. Endocast
s (casts of the inside of the skull) indicate that the neopallium part of the brain was relatively small.
s between the vertebrae that are characteristic of xenarthrans. In the seven known thoracic (chest) vertebrae, the articulations with the intervertebral disks are bean-shaped and much wider from side to side than from top to bottom. In the back thoracics and all lumbars, a longitudinal transarcual canal is present in the neural arch.
A scapula
(shoulder blade), only tentatively assigned to Plesiorycteropus, has the acromion, a process
, present, but the structure is probably not as large as in aardvarks or armadillos. Six humeri have been found; the bone is robust and an entepicondylar foramen
is present in the distal (far) end. There are three examples of the radius
, a compact and massive bone in Plesiorycteropus which resembles the pangolin radius. The three known ulna
e show that the olecranon process at the proximal (near) end is well-developed, but the distal end is narrow; the morphology of the bone suggests that the animal was capable of producing much force with its arms.
The innominate is known from seven examples, but most are quite incomplete. It includes a narrow ilium
and long ischium. The ischial tuberosity, a narrow rough piece of bone in most placentals, is broad and smooth in Plesiorycteropus. With 17 specimens, the femur is the best represented long bone. It is distinctive in its long neck, similar only to the gymnure Echinosorex according to MacPhee. A projection known as the third trochanter
is larger in P. madagascariensis. The tibia
and fibula are extensively fused into a tibiofibula, of which eight examples are known. This bone resembles that of armadillos in the extensive fusion, the compression of the shaft of the tibia, the narrowness of the articulation surface at the distal end, and the broad space between the bones. Unlike in armadillos, the tibia and fibula are not inclined relative to each other, but about parallel. The astragalus
, which is known from four examples, is wide and short and contains a uniquely large posteromedial process. Seven metapodial
s (middle hand or foot bones) are known, rather variable in size, but MacPhee was unable to separate metacarpals (from the hand) and metatarsals (from the foot). All are rather short and are broad proximally and narrow distally. Among the few known phalanges, the proximal phalange is shorter than the middle one and the distal phalanges are narrow and clawlike.
The forelimbs of Plesiorycteropus show specializations for scratch-digging, in which the forefeet are placed against the substrate, the claws are entered into the substrate, and the forefeet are then drawn back against the body. Other parts of the body also show such specializations, including large hindlimbs and a broad tail. Some aspects of the vertebral column and the pelvis suggest that the animal often assumed an erect, or sitting, posture. The animal may also have been capable of climbing, perhaps in a similar manner to gymnure
s and shrew tenrecs, which are small-eyed like Plesiorycteropus. It was probably myrmecophagous, eating insects such as ant
s and termite
s, but may also have eaten other soft food, and because of its small size probably did not forage in termite mounds, as the aardvark does.
MacPhee had material of Plesiorycteropus from twelve sites in central, western, and southern Madagascar. It and other recently extinct Madagascar mammals may have lived in and near wetlands. P. madagascariensis is known from sites throughout this range, but P. germainepetterae has only been definitely recorded from the center; small bones from southern sites may also belong to it. Thus, the two species apparently had widely overlapping ranges.
Little is known about the extinction of Plesiorycteropus, but MacPhee assumed it may have happened around 1000 years ago, when the extinction of the rest of the subfossil fauna of Madagascar is thought to have concluded. Nothing like it was reported by 17th-century European explorers of the island, and one bone has been radiocarbon dated
to around 2150 Before Present
(200 BCE). Its extinction is somewhat anomalous, as other recently extinct Madagascan animals—such as subfossil lemurs, Malagasy hippopotamus
es, the giant fossa
, and elephantbirds—were generally larger and not exclusively insectivorous; also, some species with likely more specialized diets, such as the falanouc
(Eupleres goudoti) and aye-aye
(Daubentonia robusta), did survive. Early human colonists of Madagascar may have caused the extinction of Plesiorycteropus through the destruction of the forest and other disturbances.
Eutheria
Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...
n mammalian genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
from Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. Upon its description in 1895, it was classified with the aardvark
Aardvark
The aardvark is a medium-sized, burrowing, nocturnal mammal native to Africa...
, but recent studies have found little evidence to link it to aardvarks or any other order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of mammals. Therefore, it is now placed in its own order, Bibymalagasia, which may be part of Afrotheria
Afrotheria
Afrotheria is a clade of mammals, the living members of which belong to groups from Africa or of African origin: golden moles, sengis , tenrecs, aardvarks, hyraxes, elephants and sea cows. The common ancestry of these animals was not recognized until the late 1990s...
. Two species are currently recognized, the larger P. madagascariensis and the smaller P. germainepetterae. They probably overlapped in distribution, as subfossil
Subfossil
Subfossil refers to remains whose fossilization process is not complete, either for lack of time or because the conditions in which they were buried were not optimal for fossilization....
remains of both species have been found in the same site.
Knowledge of the skeletal anatomy is limited, as only limb and partial pelvis and skull bones have been recovered to date. Plesiorycteropus was probably a digging animal that fed on insects such as termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s and ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s. It also shows adaptations for climbing and sitting. Estimates of its mass range from 6 to 18 kg (13.2 to 39.7 lb). When and why it became extinct remains unknown. One bone has been radiocarbon dated
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
to 200 BCE; forest destruction by humans may have contributed to its extinction.
Identification and species
French naturalist Henri FilholHenri Filhol
Henri Filhol was a French medical doctor, malacologist and naturalist. He served as the expedition doctor and naturalist on the French 1874 Transit of Venus expedition to Campbell Island, New Zealand, with a peak on the island, Filhol Peak, being named after him...
first described Plesiorycteropus madagascariensis in 1895 on the basis of a partial skull found at the cave of Belo
Belo sur Mer
Belo sur Mer is a town and commune in Madagascar. It belongs to the district of Morondava, which is a part of Menabe Region. The population of the commune was estimated to be approximately 8,000 in 2001 commune census....
. His description was vague even for 19th-century standards, but he placed the animal close to the aardvark
Aardvark
The aardvark is a medium-sized, burrowing, nocturnal mammal native to Africa...
(Orycteropus). The generic name combines Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
plesio- "near" with Orycteropus, the genus of the aardvark, and the specific name refers to Madagascar. Charles Lamberton, who had access to a larger sample for his 1946 review of the genus, noted substantial variation, but did not attempt to differentiate multiple species. In 1994, Ross MacPhee again reviewed Plesiorycteropus and was able to separate two species, the larger P. madagascariensis and a new, smaller species that he named Plesiorycteropus germainepetterae after scientist Germaine Petter. The two species differ in a number of morphological characters in addition to size.
Remains of Plesiorycteropus have been misidentified as rodents and primates. Charles Immanuel Forsyth Major
Charles Immanuel Forsyth Major
Charles Immanuel Forsyth Major was a Swiss zoologist and vertebrate palaeontologist.Major was born in Glasgow and studied at Basel and Zurich Universities in Switzerland and later Göttingen in Germany...
described Myoryctes rapeto in 1908 as a "giant subfossil rat" on the basis of two innominate bones (pelvic bones). The generic name was replaced by Majoria in 1915, because Myoryctes was preoccupied by the name of a nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
worm. However, according to MacPhee, innominates of Majoria are identical to those assigned to Plesiorycteropus. Guillaume Grandidier
Guillaume Grandidier
Guillaume Grandidier was a French geographer , ethnologist , zoologist who studied the island of Madagascar.He was the son of the wealthy industrialist Alfred Grandidier also a zoologist and expert on Madagascar...
assigned a well-preserved femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
(upper leg bone) to a gigantic relative of the living votsovotsa (Hypogeomys antimena), a large rodent, which he described as Hypogeomys boulei. Lamberton identified this femur as Plesiorycteropus and MacPhee concurred. Remains of both Majoria rapeto and Hypogeomys boulei fall at the upper end of the size range of the genus, indicating that they are referable to P. madagascariensis. Another Plesiorycteropus innominate was mistakenly assigned to Daubentonia robusta, the extinct giant aye-aye, and other material has been misidentified as of a dwarf lemur
Dwarf lemur
The dwarf lemurs are the lemurs of the genus Cheirogaleus. All of the species in this genus, like all other lemurs, are native to Madagascar.- Description :...
(Cheirogaleus).
Relationships
Filhol had classified Plesiorycteropus as close to the aardvark on the basis of morphological similarities. In his 1946 review, Charles Lamberton was unable to provide a definitive allocation, confused by the various similarities he saw with aardvarks, pangolinPangolin
A pangolin , also scaly anteater or Trenggiling, is a mammal of the order Pholidota. There is only one extant family and one genus of pangolins, comprising eight species. There are also a number of extinct taxa. Pangolins have large keratin scales covering their skin and are the only mammals with...
s, armadillo
Armadillo
Armadillos are New World placental mammals, known for having a leathery armor shell. Dasypodidae is the only surviving family in the order Cingulata, part of the superorder Xenarthra along with the anteaters and sloths. The word armadillo is Spanish for "little armored one"...
s, and anteater
Anteater
Anteaters, also known as antbear, are the four mammal species of the suborder Vermilingua commonly known for eating ants and termites. Together with the sloths, they compose the order Pilosa...
s. He believed it was most likely a primitive, isolated member of "Edentata", a group in which he included aardvarks, pangolins, and 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...
(sloths, armadillos, and anteaters). He rejected some alternatives, such as a close affinity to aardvarks or the possibility that the material assigned to Plesiorycteropus did not in fact represent a single animal. Bryan Patterson, who revised tubulidentates (the order of which the aardvark is the only living representative) in the 1970s, accepted Plesiorycteropus as a member of the group, dismissing many similarities with pangolins and other animals as convergent
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
. However, he placed it as the only member of its own subfamily Plesiorycteropodinae in view of its differences from other tubulidentates (subfamily Orycteropodinae), and hypothesized that it arrived on Madagascar in 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...
, at the same time as the lemur
Lemur
Lemurs are a clade of strepsirrhine primates endemic to the island of Madagascar. They are named after the lemures of Roman mythology due to the ghostly vocalizations, reflective eyes, and the nocturnal habits of some species...
s. Johannes Thewissen, who critiqued some aspects of Patterson's classification in 1985, also accepted Plesiorycteropus as a tubulidentate without comment.
Reviewing Patterson's and Thewissen's contributions in 1994, Ross MacPhee found little support for the classification of Plesiorycteropus as a tubulidentate in their data. MacPhee used a cladistic
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
analysis of eutherians to ascertain the relationships of the genus, but found that while different analytic variants supported different affinities—with aardvarks, hyrax
Hyrax
A hyrax is any of four species of fairly small, thickset, herbivorous mammals in the order Hyracoidea. The rock hyrax Procavia capensis, the yellow-spotted rock hyrax Heterohyrax brucei, the western tree hyrax Dendrohyrax dorsalis, and the southern tree hyrax, Dendrohyrax arboreus live in Africa...
es, 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 (hooved mammals), and even lipotyphlans (shrews, moles, hedgehogs, and allies)—there was no compelling evidence linking it to any other eutherian group. Therefore, he erected a separate order for Plesiorycteropus, named Bibymalagasia, arguing that it would be unacceptable to leave a Recent eutherian unassigned to any order and that discovery of more material, or further analysis, was unlikely to demonstrate close affinities of Plesiorycteropus with any other order. He considered it possible but unlikely that a few fossil taxa, such as Palaeorycteropus and Leptomanis 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...
of France, would eventually be found to be bibymalagasians. Various analyses published by Robert Asher and colleagues in 2003, 2005, and 2007, based on morphology combined with DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
data in some analyses, produced different estimates of the relationships of Plesiorycteropus, some placing it within Afrotheria
Afrotheria
Afrotheria is a clade of mammals, the living members of which belong to groups from Africa or of African origin: golden moles, sengis , tenrecs, aardvarks, hyraxes, elephants and sea cows. The common ancestry of these animals was not recognized until the late 1990s...
close to aardvarks or Afrosoricida
Afrosoricida
The order Afrosoricida contains the golden moles of southern Africa and the tenrecs of Madagascar and Africa, two families of small mammals that have traditionally been considered to be a part of the order Insectivora.Some biologists use Tenrecomorpha as the name for the tenrec-golden mole clade,...
, but others supporting a relationship with the hedgehog Erinaceus
Erinaceus
Erinaceus is a genus of European hedgehog from the family of Erinaceidae. There are four main species of Erinaceus. The range is all across Europe, throughout the Middle East, parts of Russia, and extending to northern China...
. A 2004 morphological study by Inés Horovitz, focusing on extinct South American ungulates (such as Notoungulata
Notoungulata
Notoungulata is an extinct order of hoofed, sometimes heavy bodied mammalian ungulates which inhabited South America during the Paleocene to Pleistocene, living from approximately 57 Ma to 11,000 years ago.-Taxonomy:...
and Litopterna
Litopterna
Litopterna is an extinct order of fossil hoofed mammals from the Tertiary period that displays toe reduction. Three-toed, and even a one-toed horselike form developed....
), placed Plesiorycteropus among tubulidentates and closer to the extinct aardvark relative Myorycteropus than to Orycteropus.
Common names
"Madagascar aardvark" has been used as a common nameCommon name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
for Plesiorycteropus, but MacPhee considered it inappropriate because the animal may not be related to aardvarks. Instead, he proposed "bibymalagasy" as a common name, a manufactured Malagasy
Malagasy language
Malagasy is the national language of Madagascar, a member of the Austronesian family of languages. Most people in Madagascar speak it as a first language as do some people of Malagasy descent elsewhere.-History:...
word meaning "Malagasy animal".
Description
Plesiorycteropus is known from a number of subfossilSubfossil
Subfossil refers to remains whose fossilization process is not complete, either for lack of time or because the conditions in which they were buried were not optimal for fossilization....
bones, comparable to coverage of some of the poorly known subfossil lemur
Subfossil lemur
Subfossil lemurs are lemurs from Madagascar that are represented by recent remains dating from nearly 26,000 years ago to approximately 560 years ago. They include both living and extinct species, although the term more frequently refers to the extinct giant lemurs...
s, such as Daubentonia robusta. The material includes several skulls, all of which are missing the facial bones, complete long bones such as the femur and humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
(upper arm bone), and other bones, but some elements are still unknown, including most of the skeleton of the hand and foot. There is little reason to assume it was similar in general form to the aardvark. No teeth or jaws referable to Plesiorycteropus have been found, and it is generally assumed that the animal was toothless.
Based on the area of a femur cross-section, MacPhee calculated estimates of body mass. The lowest estimate, based on comparative data from armadillos and pangolins, was 6 kilograms (13.2 lb) for the smallest femur he had (referable to P. germainepetterae) and the highest estimate, based on comparative data from caviomorph rodents, was 18 kilograms (39.7 lb) for the largest available femur (P. madagascariensis); estimates from primates fell between those extremes. MacPhee favored the lower estimates, because those were based on armadillos, which have femora similar to those of Plesiorycteropus. On the other hand, the caviomorph model produced a better estimate of brain size in Plesiorycteropus.
Skull
There are four known skulls (three of P. madagascariensis and one of P. germainepetterae), each of which is damaged. All are missing the front (rostral) part, and three are broken at about the same place (at the paranasal cavities, at the front of the braincase), suggesting that the front part of the skull was thinner and more fragile than the back part, which consists of thick bones. MacPhee estimated maximum skull length in P. madagascariensis at 101 millimetres (4 in). The length of the frontal boneFrontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
averages 35.4 millimetres (1.4 in) in P. madagascariensis and is 29.4 millimetres (1.2 in) in P. germainepetterae.
The robust nasal bone
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
s, preserved in a single specimen, are widest at the front, a feature unusual among placentals that is also seen in armadillos, and are also unusually flat. The ethmoid labyrinth, in the nasal cavity
Nasal cavity
The nasal cavity is a large air filled space above and behind the nose in the middle of the face.- Function :The nasal cavity conditions the air to be received by the other areas of the respiratory tract...
, was large, suggesting that Plesiorycteropus had a good sense of smell. A much larger part of the nasal septum
Nasal septum
The nasal septum separates the left and right airways in the nose, dividing the two nostrils.It is depressed by the Depressor septi nasi muscle.-Composition:The fleshy external end of the nasal septum is sometimes also called columella....
, which separates the left and right nasal cavities, is ossified than usual in other mammals; MacPhee could find a similar condition only in sloths, which have a very short nose. The lacrimal bone
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
is relatively large. At it is a single lacrimal canal, which opens near the suture
Suture (anatomical)
In anatomy, a suture is a fairly rigid joint between two or more hard elements of an animal, with or without significant overlap of the elements....
between the frontal and lacrimal bones, like in lipotyphlans. There is a small tubercle (absent in aardvarks) near this opening. The orbital cavity, which houses the eyes, is relatively short, similar to the situation in pangolins and armadillos. A distinct tubercle is present on the suture between the frontal and parietal bone
Parietal bone
The parietal bones are bones in the human skull which, when joined together, form the sides and roof of the cranium. Each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin pariet-, wall....
s in P. germainepetterae, but not P. madagascariensis. P. madagascariensis has a more expansive braincase and a less pronounced narrowing between the orbits. The foramen rotundum
Foramen rotundum
The foramen rotundum is a circular hole in the sphenoid bone that connects the middle cranial fossa and the pterygopalatine fossa.-Structure:...
, an opening in the bone of the orbit, is present. The optic canal, which houses the nerves leading to the eyes, is narrow, suggesting that the eyes were small. As in pangolins and xenarthrans, little of the squamosal bone can be seen from above. The temporal line
Temporal line
Crossing the middle of the parietal bone in an arched direction are two curved lines, the superior and inferior temporal lines; the former gives attachment to the temporal fascia, and the latter indicates the upper limit of the muscular origin of the Temporalis.-External links:*...
s on the braincase, which anchor muscles, are located lower in P. germainepetterae. Like in aardvarks, the parietals are relatively large. An interparietal bone is present. Unlike in anteaters and pangolins, the occiput
Occiput
The occiput is the anatomical term for the posterior portion of the head, in insects the posterior part of those head capsule.-Clinical significance:Trauma to the occiput can cause a basilar skull fracture....
(the back of the skull) is flat and vertical. Plesiorycteropus lacks notches above the foramen magnum (the opening that connects the brain to the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
), which are present in aardvarks. The nuchal crest, a projection on the occiput, is straight in P. madagascariensis, but in P. germainepetterae it is interrupted in the middle, similar to the situation in armadillos and hyraxes.
In their descriptions of Plesiorycteropus, Lamberton and Patterson posited different interpretations of the location of the mandibular fossa
Mandibular fossa
The mandibular fossa is the depression in the temporal bone that articulates with the mandibular condyle. In the temporal bone, the mandibular fossa is bounded, in front, by the articular tubercle; behind, by the tympanic part of the bone, which separates it from the external acoustic meatus; it is...
, where the mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
(lower jaw) articulates with the cranium. MacPhee found problems with either interpretation and suggested that the true mandibular fossa was part of the area Lamberton identified as such, at the side of the braincase. The fossa is small and low, suggesting that the animal was not capable of powerful biting. At the back of this fossa is a pseudoglenoid proces, which is more prominent in P. germainepetterae. In P. germainepetterae but not P. madagascariensis, a small opening, perhaps the vascular foramen, is present next to the foramen ovale
Foramen ovale (skull)
At the base of the skull the foramen ovale is one of the larger of the several holes that transmit nerves through the skull. The foramen ovale is situated in the posterior part of the sphenoid bone, posterolateral to the foramen rotundum.-Contents:Several nerves, arteries and veins pass through...
. The petrosal bone forms a relatively large portion of the roof of the tympanic cavity
Tympanic cavity
The tympanic cavity is a small cavity surrounding the bones of the middle ear.It is formed from the tubotympanic recess, an expansion of the first pharyngeal pouch....
, which houses the middle ear; parts of the petrosal are more developed in P. madagascariensis. Endocast
Endocast
An endocast is the internal cast of a hollow object, often specifically used for an endocasts of the cranial vault. Endocasts can be man-made for examining the properties of a hollow, inaccessible space, or occur naturally through fossilisation....
s (casts of the inside of the skull) indicate that the neopallium part of the brain was relatively small.
Postcranium
There are 34 known vertebrae of Plesiorycteropus. The animal had at least seven sacral and five or six lumbar vertebrae. A find of associated caudal vertebrae from the base of the tail, which diminish in size only slowly from front to back, suggests that the tail was long. There is no evidence for the additional jointJoint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...
s between the vertebrae that are characteristic of xenarthrans. In the seven known thoracic (chest) vertebrae, the articulations with the intervertebral disks are bean-shaped and much wider from side to side than from top to bottom. In the back thoracics and all lumbars, a longitudinal transarcual canal is present in the neural arch.
A scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
(shoulder blade), only tentatively assigned to Plesiorycteropus, has the acromion, a process
Process (anatomy)
In anatomy, a process is a projection or outgrowth of tissue from a larger body. The vertebra has several kinds of processes,such as: transverse process, prezygapophysis, postzygapophysis.-Examples:Examples of processes include:...
, present, but the structure is probably not as large as in aardvarks or armadillos. Six humeri have been found; the bone is robust and an entepicondylar foramen
Entepicondylar foramen
The entepicondylar foramen is an opening in the distal end of the humerus present in some mammals. It is often present in primitive placentals, such as the enigmatic Madagascan Plesiorycteropus...
is present in the distal (far) end. There are three examples of the radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
, a compact and massive bone in Plesiorycteropus which resembles the pangolin radius. The three known ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
e show that the olecranon process at the proximal (near) end is well-developed, but the distal end is narrow; the morphology of the bone suggests that the animal was capable of producing much force with its arms.
The innominate is known from seven examples, but most are quite incomplete. It includes a narrow ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...
and long ischium. The ischial tuberosity, a narrow rough piece of bone in most placentals, is broad and smooth in Plesiorycteropus. With 17 specimens, the femur is the best represented long bone. It is distinctive in its long neck, similar only to the gymnure Echinosorex according to MacPhee. A projection known as the third trochanter
Third trochanter
In human anatomy, the third trochanter is a bony projection occasionally present on the proximal femur near the superior border of the gluteal tuberosity. When present, it is oblong, rounded, or conical in shape and sometimes continuous with the gluteal ridge...
is larger in P. madagascariensis. The tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
and fibula are extensively fused into a tibiofibula, of which eight examples are known. This bone resembles that of armadillos in the extensive fusion, the compression of the shaft of the tibia, the narrowness of the articulation surface at the distal end, and the broad space between the bones. Unlike in armadillos, the tibia and fibula are not inclined relative to each other, but about parallel. The astragalus
Talus bone
-External links:* *...
, which is known from four examples, is wide and short and contains a uniquely large posteromedial process. Seven metapodial
Metapodial
Metapodials are long bones of the hand and feet which connect the digits to the centers. In humans, five are present in each hand and foot....
s (middle hand or foot bones) are known, rather variable in size, but MacPhee was unable to separate metacarpals (from the hand) and metatarsals (from the foot). All are rather short and are broad proximally and narrow distally. Among the few known phalanges, the proximal phalange is shorter than the middle one and the distal phalanges are narrow and clawlike.
Ecology, behavior, and extinction
| Site | ger. | mad. | sp. |
|---|---|---|---|
| Ambolisatra | + | + | |
| Ampasambazimba | + | + | + |
| Ampoza | + | ||
| Anjohibe | + | + | |
| Ankevo | ? | ||
| Anovaha | + | ||
| Antsirabe Antsirabe Antsirabe is the third largest city in Madagascar and has a population of approximately 183,000. It's the capital of the Vakinankaratra region... |
+ | + | |
| Belo Belo sur Mer Belo sur Mer is a town and commune in Madagascar. It belongs to the district of Morondava, which is a part of Menabe Region. The population of the commune was estimated to be approximately 8,000 in 2001 commune census.... |
+ | ||
| Bemifany | + | ||
| Masinandraina | + | ||
| Sirave | + | ||
Abbreviations:
|
|||
The forelimbs of Plesiorycteropus show specializations for scratch-digging, in which the forefeet are placed against the substrate, the claws are entered into the substrate, and the forefeet are then drawn back against the body. Other parts of the body also show such specializations, including large hindlimbs and a broad tail. Some aspects of the vertebral column and the pelvis suggest that the animal often assumed an erect, or sitting, posture. The animal may also have been capable of climbing, perhaps in a similar manner to gymnure
Gymnure
The gymnure, also called a hairy hedgehog or moonrat, is a type of mammal belonging to the subfamily Galericinae, in the family Erinaceidae and the order Erinaceomorpha...
s and shrew tenrecs, which are small-eyed like Plesiorycteropus. It was probably myrmecophagous, eating insects such as ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s and termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s, but may also have eaten other soft food, and because of its small size probably did not forage in termite mounds, as the aardvark does.
MacPhee had material of Plesiorycteropus from twelve sites in central, western, and southern Madagascar. It and other recently extinct Madagascar mammals may have lived in and near wetlands. P. madagascariensis is known from sites throughout this range, but P. germainepetterae has only been definitely recorded from the center; small bones from southern sites may also belong to it. Thus, the two species apparently had widely overlapping ranges.
Little is known about the extinction of Plesiorycteropus, but MacPhee assumed it may have happened around 1000 years ago, when the extinction of the rest of the subfossil fauna of Madagascar is thought to have concluded. Nothing like it was reported by 17th-century European explorers of the island, and one bone has been radiocarbon dated
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
to around 2150 Before Present
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
(200 BCE). Its extinction is somewhat anomalous, as other recently extinct Madagascan animals—such as subfossil lemurs, Malagasy hippopotamus
Malagasy Hippopotamus
Several species of Malagasy Hippopotamus lived on the island of Madagascar but are now believed to be extinct. The animals were very similar to the extant Hippopotamus and Pygmy Hippopotamus...
es, the giant fossa
Cryptoprocta spelea
Cryptoprocta spelea, also known as the giant fossa, is an extinct species of carnivore from Madagascar in the family Eupleridae, which is most closely related to the mongooses and includes all Malagasy carnivorans. It was first described in 1902, and in 1935 was recognized as a separate species...
, and elephantbirds—were generally larger and not exclusively insectivorous; also, some species with likely more specialized diets, such as the falanouc
Falanouc
The Falanouc is a rare mongoose-like mammal endemic Malagasy euplerid .It is classified alongside its closest living relative, the Fanaloka, in the subfamily Euplerinae. The Falanouc has several peculiarities which merit its independent classification...
(Eupleres goudoti) and aye-aye
Aye-aye
The aye-aye is a lemur, a strepsirrhine primate native to Madagascar that combines rodent-like teeth and a special thin middle finger to fill the same ecological niche as a woodpecker...
(Daubentonia robusta), did survive. Early human colonists of Madagascar may have caused the extinction of Plesiorycteropus through the destruction of the forest and other disturbances.
See also
- List of mammals of Madagascar
- NecrolestesNecrolestesNecrolestes patagonensis is an extinct mammal, possibly a marsupial, that lived in the early Miocene of South America....
– another "mystery mammal", from the early MioceneMioceneThe Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
of ArgentinaArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
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