Fruitafossor
Encyclopedia
Fruitafossor was a termite
-eating mammal
endemic to North America
during the Late Jurassic
epoch (155.7—150.8 mya), existing for approximately .
The description is based on a surprisingly complete skeleton of a chipmunk
-sized animal. It was discovered on March 31, 2005, in Fruita, Colorado
. It resembled an armadillo
(or anteater
) and probably ate colonial insects in much the same manner as these animals do today. Other skeletal features clearly show that Fruitafossor was not related to armadillos, anteaters, or any modern group of mammal. This indicates that specializations associated with feeding on ants or termites have independently evolved many times in mammals: in Fruitafossor, anteaters, numbat
s, aardvark
s, pangolin
s, and spiny anteaters
.
by using
the ratio of dentary length to body mass of modern marsupials as a reference. Foster concludes that Fruitafossor was the least massive of the formation at 6g, much lower than the average Morrison mammal of 48.5g.
." Since ant
s had not yet evolved at the time of Fruitafossor, it is assumed that these animals fed on termite
s, which were abundant along with their relatives the cockroach
es.
Fruitafossor has been nicknamed Popeye
, after the cartoon sailor, because of its large front limbs. The features of the front limb indicate that the animal was fossorial
, employing scratch digging like modern moles
, gopher
s, and spiny anteaters. The olecranon
process was highly enlarged indicating the forelimb had powerful muscles. This feature also supports the idea that they were myrmecophagous, as modern mammals employ this technique to break into termite mounds.
Its vertebral column is also very similar to armadillos, sloths, and anteaters (order Xenarthra
). It had extra points of contact among vertebrae similar to the xenarthrous process that are only known in these modern forms. These processes generate a rigid and relatively inflexible backbone, which is good for digging.
This find is an important discovery in mammal evolution, because of where it fits in the evolutionary tree of mammals and because of its ecological niche
. Most mammals of the Mesozoic
were omnivore
s or unspecialized insectivore
s. Fruitafossor is unique in the degree of specialization, both for digging and in regard to how specialized it was on insects. This fossil, along with others such as Repenomamus
, Volaticotherium, and Castorocauda
, challenge the notion that early mammals and mammaliaforms were restricted to a single niche and demonstrate that at least some early specialization occurred.
ns (the subclass containing marsupial
s and placentals). It has a unique suite of therian and prototheria
n characteristics. Its shoulder-girdle is similar to a platypus
or reptile
, but many other features are more similar to most other modern mammals. This has led researchers to suggest that it may have been the earliest known relative to the evolutionary line leading to Theria.
The genus name, Fruitafossor, comes from Fruita, Colorado, where it was discovered. The "fossor" indicates the fossorial, or digging, specialization of the forelimbs. The specific epithet, windscheffeli, is in honor of Wally Windscheffel, who discovered the specimen along with C. Safris.
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...
-eating mammal
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...
endemic to North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
during the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
epoch (155.7—150.8 mya), existing for approximately .
The description is based on a surprisingly complete skeleton of a chipmunk
Chipmunk
Chipmunks are small striped squirrels native to North America and Asia. They are usually classed either as a single genus with three subgenera, or as three genera.-Etymology and taxonomy:...
-sized animal. It was discovered on March 31, 2005, in Fruita, Colorado
Fruita, Colorado
The City of Fruita is a Home Rule Municipality located in the western part of Mesa County, Colorado, in the United States. It is part of the Grand Junction Metropolitan Statistical Area and within the Grand Valley...
. It resembled an 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"...
(or 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...
) and probably ate colonial insects in much the same manner as these animals do today. Other skeletal features clearly show that Fruitafossor was not related to armadillos, anteaters, or any modern group of mammal. This indicates that specializations associated with feeding on ants or termites have independently evolved many times in mammals: in Fruitafossor, anteaters, numbat
Numbat
The numbat , also known as the banded anteater, or walpurti, is a marsupial found in Western Australia. Its diet consists almost exclusively of termites. Once widespread across southern Australia, the range is now restricted to several small colonies and it is listed as an endangered species...
s, aardvark
Aardvark
The aardvark is a medium-sized, burrowing, nocturnal mammal native to Africa...
s, pangolin
Pangolin
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, and spiny anteaters
Echidna
Echidnas , also known as spiny anteaters, belong to the family Tachyglossidae in the monotreme order of egg-laying mammals. There are four extant species, which, together with the platypus, are the only surviving members of that order and are the only extant mammals that lay eggs...
.
Description
In 2009, a study by J. R. Foster was published that estimated the body masses of mammals from the Late Jurassic Morrison FormationMorrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
by using
Regression analysis
In statistics, regression analysis includes many techniques for modeling and analyzing several variables, when the focus is on the relationship between a dependent variable and one or more independent variables...
the ratio of dentary length to body mass of modern marsupials as a reference. Foster concludes that Fruitafossor was the least massive of the formation at 6g, much lower than the average Morrison mammal of 48.5g.
Armadillo teeth and Popeye arms
The teeth of Fruitafossor bear a striking resemblance to modern armadillos and aardvarks. They were open-rooted, peg-like teeth without enamel. This type of tooth is present today in insectivorous mammals, particularly those that are highly specialized to feed on colonial insects. This is termed "myrmecophagyMyrmecophagy
Myrmecophagy is a feeding behavior defined by the consumption of termites or ants, particularly in those animal species whose diets are largely or exclusively composed of said insect types....
." Since 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 had not yet evolved at the time of Fruitafossor, it is assumed that these animals fed on 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, which were abundant along with their relatives the cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
es.
Fruitafossor has been nicknamed Popeye
Popeye
Popeye the Sailor is a cartoon fictional character created by Elzie Crisler Segar, who has appeared in comic strips and animated cartoons in the cinema as well as on television. He first appeared in the daily King Features comic strip Thimble Theatre on January 17, 1929...
, after the cartoon sailor, because of its large front limbs. The features of the front limb indicate that the animal was fossorial
Fossorial
A fossorial organism is one that is adapted to digging and life underground such as the badger, the naked mole rat, and the mole salamanders Ambystomatidae...
, employing scratch digging like modern moles
Mole (animal)
Moles are small cylindrical mammals adapted to a subterranean lifestyle. They have velvety fur; tiny or invisible ears and eyes; and short, powerful limbs with large paws oriented for digging. The term is especially and most properly used for the true moles, those of the Talpidae family in the...
, gopher
Gopher (animal)
The term gopher as it is commonly used does not relate to any one species, but is a generic term used to describe any of several small burrowing rodents endemic to North America, including the pocket gopher , also called true gophers, and the ground squirrel , including Richardson's ground squirrel...
s, and spiny anteaters. The olecranon
Olecranon
The olecranon is a large, thick, curved bony eminence of the forearm that projects behind the elbow.It is situated at the upper end of the ulna, one of the two bones in the forearm...
process was highly enlarged indicating the forelimb had powerful muscles. This feature also supports the idea that they were myrmecophagous, as modern mammals employ this technique to break into termite mounds.
Its vertebral column is also very similar to armadillos, sloths, and anteaters (order 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...
). It had extra points of contact among vertebrae similar to the xenarthrous process that are only known in these modern forms. These processes generate a rigid and relatively inflexible backbone, which is good for digging.
This find is an important discovery in mammal evolution, because of where it fits in the evolutionary tree of mammals and because of its ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
. Most mammals of the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
were omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
s or unspecialized insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
s. Fruitafossor is unique in the degree of specialization, both for digging and in regard to how specialized it was on insects. This fossil, along with others such as Repenomamus
Repenomamus
Repenomamus is the largest mammal known from the Cretaceous period of Manchuria, and it is the mammal for which there is the best evidence that it fed on dinosaurs. It is not possible to determine if Repenomamus actively hunted live dinosaurs or scavenged dead dinosaurs.-Paleobiology:Repenomamus...
, Volaticotherium, and Castorocauda
Castorocauda lutrasimilis
Castorocauda was a genus of small, semi-aquatic relative of mammals living in the mid Jurassic period, around 154 million years ago, found in lakebed sediments of the Daohugou Beds of Inner Mongolia...
, challenge the notion that early mammals and mammaliaforms were restricted to a single niche and demonstrate that at least some early specialization occurred.
To what is it related?
Fruitafossor has no modern relatives. It is an early offshoot of mammal related to theriaTheria
Theria is a subclass of mammals that give birth to live young without using a shelled egg, including both eutherians and metatherians . The only omitted extant mammal group is the egg-laying monotremes....
ns (the subclass containing 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 placentals). It has a unique suite of therian and prototheria
Prototheria
Prototheria is a taxonomic group, or taxon, to which the order Monotremata belongs. It is conventionally ranked as a subclass within the mammals.Most of the animals in this group are extinct...
n characteristics. Its shoulder-girdle is similar to a platypus
Platypus
The platypus is a semi-aquatic mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young...
or reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
, but many other features are more similar to most other modern mammals. This has led researchers to suggest that it may have been the earliest known relative to the evolutionary line leading to Theria.
The genus name, Fruitafossor, comes from Fruita, Colorado, where it was discovered. The "fossor" indicates the fossorial, or digging, specialization of the forelimbs. The specific epithet, windscheffeli, is in honor of Wally Windscheffel, who discovered the specimen along with C. Safris.
See also
- Morrison FormationMorrison FormationThe Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
- Mammals of the Morrison Formation