Paluxysaurus
Encyclopedia
Paluxysaurus is a genus
of basal
titanosauriform sauropod dinosaur
from the late Aptian
or early Albian
-age (around 112 million years old) Lower Cretaceous Twin Mountains Formation
of Hood County, Texas, USA. It is known from the remains of at least four individuals found in a bonebed.
that suggested Paluxysaurus formed a clade
with Brachiosaurus
, which would make it a brachiosaurid
. The clade, though, is only supported by a single characteristic
: a "relatively transversely
broad femur
at mid-shaft". Whether or not it is a brachiosaurid, Paluxysaurus appears to be a basal titanosauriform.
, above the Twin Mountains Formation). In the mid 1980s, students from the University of Texas at Austin
discovered a bonebed on a ranch in Hood County, but early work stopped in 1987. The quarry was reopened in 1993 and has been worked since then, by parties from Southern Methodist University
, the Fort Worth Museum of Science and History
, and Tarleton State University
. All sauropod remains appear to come from the same genus of sauropod. Petrified logs
are also known from the site. The discovery site was fluvial
when its rocks were being deposited, with channel sands and muds, and concretion
s of calcite
-cemented sandstone
containing fossils. Following excavation and preparation of the majority of the fossils, the sauropod has been named Paluxysaurus.
Paluxysaurus is based on
FWMSH 93B-10-18, an associated left maxilla
and nasal
, and teeth. Other bones from the quarry include a partial neck of seven vertebrae, thirteen vertebrae from the back and 30 from the tail, and examples of all limb and girdle bones except some hand and foot bones. It is distinguished
from all other sauropods by vertebral details, and has various morphological
differences in other bones compared to other sauropods of the Early Cretaceous of North America. The genus has so far been limited to the bonebed remains; for example, the partial skeleton from Wise County
known as Pleurocoelus sp. (SMU
61732) is not referred to Paluxysaurus. There are differences in the remains of P. sp. and Paluxysaurus, but they cannot be distinguished with confidence.
al herbivore
, eating plants with a small head on a long neck.
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 basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
titanosauriform sauropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the late Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
or early Albian
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
-age (around 112 million years old) Lower Cretaceous Twin Mountains Formation
Twin Mountains Formation
The Twin Mountains Formation, also known as the Twin Mountain Formation, is a sedimentary rock formation, within the Trinity Group, found in Texas of the United States of America. It is a terrestrial formation of Aptian age , and is notable for its dinosaur fossils...
of Hood County, Texas, USA. It is known from the remains of at least four individuals found in a bonebed.
Classification
Peter J. Rose, who described the genus, performed a cladistic analysisCladistics
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...
that suggested Paluxysaurus formed a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
with Brachiosaurus
Brachiosaurus
Brachiosaurus is a genus of sauropod dinosaur from the Jurassic Morrison Formation of North America. It was first described by Elmer S. Riggs in 1903 from fossils found in the Grand River Canyon of western Colorado, in the United States. Riggs named the dinosaur Brachiosaurus altithorax,...
, which would make it a brachiosaurid
Brachiosauridae
Brachiosauridae are a family of dinosaurs, whose members are known as brachiosaurids. They were herbivorous quadrupeds with longer forelegs than hind legs - the name derives from the Greek for arm lizard - and long necks...
. The clade, though, is only supported by a single characteristic
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
: a "relatively transversely
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
broad 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...
at mid-shaft". Whether or not it is a brachiosaurid, Paluxysaurus appears to be a basal titanosauriform.
Discovery and history
Sauropod bones and trackways have long been known from the Paluxy River area, usually referred to the genus Pleurocoelus, including partial skeletons (particularly from the Glen Rose FormationGlen Rose Formation
The Glen Rose Formation is a shallow marine to shoreline geological formation from the lower Cretaceous period exposed over a large area from South Central to North Central Texas...
, above the Twin Mountains Formation). In the mid 1980s, students from the University of Texas at Austin
University of Texas at Austin
The University of Texas at Austin is a state research university located in Austin, Texas, USA, and is the flagship institution of the The University of Texas System. Founded in 1883, its campus is located approximately from the Texas State Capitol in Austin...
discovered a bonebed on a ranch in Hood County, but early work stopped in 1987. The quarry was reopened in 1993 and has been worked since then, by parties from Southern Methodist University
Southern Methodist University
Southern Methodist University is a private university in Dallas, Texas, United States. Founded in 1911 by the Methodist Episcopal Church, South, SMU operates campuses in Dallas, Plano, and Taos, New Mexico. SMU is owned by the South Central Jurisdiction of the United Methodist Church...
, the Fort Worth Museum of Science and History
Fort Worth Museum of Science and History
The Fort Worth Museum of Science and History is located on 1600 Gendy Street, Fort Worth, Texas 76107 in the city's Cultural District. It was opened in 1945 as the Fort Worth Children's Museum and moved to its current location in 1954. In 1968, the museum adopted its current name...
, and Tarleton State University
Tarleton State University
Tarleton State University is a public, coeducational, state university located in Stephenville, Texas. It is the largest non-land-grant university primarily devoted to agriculture in the United States....
. All sauropod remains appear to come from the same genus of sauropod. Petrified logs
Petrified wood
Petrified wood is the name given to a special type of fossilized remains of terrestrial vegetation. It is the result of a tree having turned completely into stone by the process of permineralization...
are also known from the site. The discovery site was fluvial
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
when its rocks were being deposited, with channel sands and muds, and concretion
Concretion
A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity . Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and crescere meaning 'to grow'...
s of calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
-cemented sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
containing fossils. Following excavation and preparation of the majority of the fossils, the sauropod has been named Paluxysaurus.
Paluxysaurus is based on
Holotype
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...
FWMSH 93B-10-18, an associated left 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...
and nasal
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....
, and teeth. Other bones from the quarry include a partial neck of seven vertebrae, thirteen vertebrae from the back and 30 from the tail, and examples of all limb and girdle bones except some hand and foot bones. It is distinguished
Autapomorphy
In cladistics, an autapomorphy is a distinctive anatomical feature, known as a derived trait, that is unique to a given terminal group. That is, it is found only in one member of a clade, but not found in any others or outgroup taxa, not even those most closely related to the group...
from all other sauropods by vertebral details, and has various morphological
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....
differences in other bones compared to other sauropods of the Early Cretaceous of North America. The genus has so far been limited to the bonebed remains; for example, the partial skeleton from Wise County
Wise County, Texas
As of the census of 2000, there were 48,793 people, 17,178 households, and 13,467 families residing in the county. The population density was 54 people per square mile . There were 19,242 housing units at an average density of 21 per square mile...
known as Pleurocoelus sp. (SMU
Southern Methodist University
Southern Methodist University is a private university in Dallas, Texas, United States. Founded in 1911 by the Methodist Episcopal Church, South, SMU operates campuses in Dallas, Plano, and Taos, New Mexico. SMU is owned by the South Central Jurisdiction of the United Methodist Church...
61732) is not referred to Paluxysaurus. There are differences in the remains of P. sp. and Paluxysaurus, but they cannot be distinguished with confidence.
Paleoecology and paleobiology
Like other sauropods, Paluxysaurus would have been a large, quadrupedQuadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, eating plants with a small head on a long neck.