Wannaganosuchus
Encyclopedia
Wannaganosuchus is an extinct genus
of small alligatorid
. It was found in late Paleocene
-age rocks of Billings County
, North Dakota
, United States
.
SMM
P76.28.247, a mostly complete skull and postcrania
l skeleton missing some vertebrae, coracoids, part of the feet, ribs, and other pieces. A few small bony scutes
are also assigned to the genus, but not to the type specimen. SMM P76.28.247 was found semi-articulated in the lower part of the Bullion Creek Formation, near the base of a lignitic
clay layer deposited in a marsh
setting on a floodplain. Wannaganosuchus was named in 1982 by Bruce R. Erickson
. The type species
is W. brachymanus; the specific name means "short forefoot".
The skull of SMM P76.28.247 was low, without elevated rims over the eyes, and was 159 millimetres (6.3 in) long. The snout was short and pointed compared to Cretaceous
alligatorids. Its premaxilla
e (the bones of the tip of the snout) had five teeth each, while the maxilla
e (main tooth-bearing bones of the upper jaw) had thirteen teeth each, with the fourth being the largest and the last three having broad flattened crowns. The lower jaws had twenty teeth on each side, and like the upper jaws, the last five had broad crushing crowns. The forelimbs were short (hence the specific name), and the hindlimbs were long in comparison. The scutes were extensive. Most of the scutes were keeled, but did not have spikes.
Erickson regarded Wannaganosuchus as a generalized early alligatorid closer to the line leading to modern alligatorids than other more specialized early alligatorids. It may be the same as Allognathosuchus
.
logs are common. The deposit was formed under 2 to 3 m (6.6 to 9.8 ft) of water, and grades into a shoreline deposit about 20 metres (65.6 ft) away. Lilies
and water ferns grew along the shore and were shaded by cypress
trees.
SMM P76.28.247 was found in direct association with skeletons of Borealosuchus formidabilis
and the long-snouted champsosaur
Champsosaurus
. These three taxa probably occupied different ecological niche
s based on size and morphology
. Wannaganosuchus was a small alligatorid, only about 1 metres (3.3 ft) long as an adult, much smaller than its more abundant distant relative from the same quarry, Borealosuchus (roughly 4 metres (13.1 ft) long). Borealosuchus would have dominated the beach zone, while Champsosaurus is interpreted as a piscivore
that swam near the bottom. Wannaganosuchus is thought to have lived like the modern caiman Paleosuchus
, preferring seclusion. It may have floated among clumps of water plants. The structure of the arms, legs, and tail suggest that it was more aquatic than terrestrial. The mix of tooth shapes indicate it could eat a variety of foods.
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...
of small alligatorid
Alligatoridae
Alligatoridae is a family of crocodylians that includes alligators and caimans.- True alligators :Alligators proper occur in the fluvial deposits of the age of the Upper Chalk in Europe, where they did not die out until the Pliocene age. The true alligators are now restricted to two species, A...
. It was found in late Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
-age rocks of Billings County
Billings County, North Dakota
-National protected areas:* Little Missouri National Grassland * Theodore Roosevelt National Park -Demographics:As of the census of 2000, there were 888 people, 366 households, and 255 families residing in the county. The population density was 0.79 people per square mile . There were 529 housing...
, North Dakota
North Dakota
North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
History and description
Wannaganosuchus is based onHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
SMM
Science Museum of Minnesota
The Science Museum of Minnesota is an American museum focused on topics in technology, natural history, physical science and mathematics education. Founded in 1907 and located in Saint Paul, Minnesota, the 501 nonprofit institution is staffed by over 500 employees and over 1,600 volunteers...
P76.28.247, a mostly complete skull and postcrania
Postcrania
Postcrania[p] in zoology and vertebrate paleontology refers to all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g...
l skeleton missing some vertebrae, coracoids, part of the feet, ribs, and other pieces. A few small bony scutes
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
are also assigned to the genus, but not to the type specimen. SMM P76.28.247 was found semi-articulated in the lower part of the Bullion Creek Formation, near the base of a lignitic
Lignite
Lignite, often referred to as brown coal, or Rosebud coal by Northern Pacific Railroad,is a soft brown fuel with characteristics that put it somewhere between coal and peat...
clay layer deposited in a marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
setting on a floodplain. Wannaganosuchus was named in 1982 by Bruce R. Erickson
Bruce Erickson (paleontologist)
Bruce R. Erickson is an American paleontologist and former Chair of Paleontology at the Science Museum of Minnesota. He retired as Chair of Paleontology in 1996. During the course of his lifetime and his 44 years as a paleontologist, he has "collected about a million specimens" and discovered...
. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is W. brachymanus; the specific name means "short forefoot".
The skull of SMM P76.28.247 was low, without elevated rims over the eyes, and was 159 millimetres (6.3 in) long. The snout was short and pointed compared to 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...
alligatorids. Its premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
e (the bones of the tip of the snout) had five teeth each, while the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e (main tooth-bearing bones of the upper jaw) had thirteen teeth each, with the fourth being the largest and the last three having broad flattened crowns. The lower jaws had twenty teeth on each side, and like the upper jaws, the last five had broad crushing crowns. The forelimbs were short (hence the specific name), and the hindlimbs were long in comparison. The scutes were extensive. Most of the scutes were keeled, but did not have spikes.
Erickson regarded Wannaganosuchus as a generalized early alligatorid closer to the line leading to modern alligatorids than other more specialized early alligatorids. It may be the same as Allognathosuchus
Allognathosuchus
Allognathosuchus is an extinct genus of alligatorine crocodylian with a complicated taxonomic history. This small alligatorine is known for its stout jaws and bulbous teeth, found near the rear of the tooth row in upper and lower jaws. These adaptations have historically been interpreted as...
.
Paleoecology and paleobiology
Wannaganosuchus was found in a layer with abundant plant fossils suggesting the presence of a swamp forest in the area; taxodioidTaxodium
Taxodium is a genus of one to three species of extremely flood-tolerant conifers in the cypress family, Cupressaceae...
logs are common. The deposit was formed under 2 to 3 m (6.6 to 9.8 ft) of water, and grades into a shoreline deposit about 20 metres (65.6 ft) away. Lilies
Lilium
Lilium is a genus of herbaceous flowering plants growing from bulbs. Most species are native to the temperate northern hemisphere, though the range extends into the northern subtropics...
and water ferns grew along the shore and were shaded by cypress
Cypress
Cypress is the name applied to many plants in the cypress family Cupressaceae, which is a conifer of northern temperate regions. Most cypress species are trees, while a few are shrubs...
trees.
SMM P76.28.247 was found in direct association with skeletons of Borealosuchus formidabilis
Borealosuchus
Borealosuchus is an extinct genus of crocodilian that lived from the Late Cretaceous to the Eocene in North America. It was named by Chris Brochu in 1997 for several species that had been assigned to Leidyosuchus. The species assigned to it are:B...
and the long-snouted champsosaur
Choristodera
Choristodera is an order of semi-aquatic diapsid reptiles which ranged from the Middle Jurassic, or possibly Late Triassic, to at least the early Miocene. Choristoderes have been found in North America, Asia, and Europe. The most common fossils are typically found from the Late Cretaceous to the...
Champsosaurus
Champsosaurus
Champsosaurus is an extinct genus of diapsid reptile belonging to the order Choristodera. It grew to about 1.50 m long....
. These three taxa probably occupied different 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...
s based on size and morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
. Wannaganosuchus was a small alligatorid, only about 1 metres (3.3 ft) long as an adult, much smaller than its more abundant distant relative from the same quarry, Borealosuchus (roughly 4 metres (13.1 ft) long). Borealosuchus would have dominated the beach zone, while Champsosaurus is interpreted as a piscivore
Piscivore
A piscivore is a carnivorous animal which eats primarily fish. Piscivory was the diet of early tetrapods , insectivory came next, then in time reptiles added herbivory....
that swam near the bottom. Wannaganosuchus is thought to have lived like the modern caiman Paleosuchus
Paleosuchus
Paleosuchus is a South American genus of reptile in the Alligatoridae family. They are the smallest members of the order Crocodilia in the Americas.The genus contains two species:* Cuvier's Dwarf Caiman ....
, preferring seclusion. It may have floated among clumps of water plants. The structure of the arms, legs, and tail suggest that it was more aquatic than terrestrial. The mix of tooth shapes indicate it could eat a variety of foods.