Pawpawsaurus
Encyclopedia
Pawpawsaurus, meaning "Pawpaw Lizard", is a nodosaurid ankylosaur from the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 (late 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...

) of Tarrant County, Texas
Tarrant County, Texas
Tarrant County is a county located in the U.S. state of Texas. As of the 2010 U.S. Census, it had a population of 1,809,034. Its county seat is Fort Worth. Tarrant County is the sixteenth most populous county in the United States and the third most populous in Texas. The county is named in honor...

, discovered in May 1992. The only species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 yet assigned to this taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

, Pawpawsaurus campbelli, is based on a complete skull (lacking mandibles) from the marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 Paw Paw Formation (Wachita Group). The Paw Paw Formation has produced another nodosaurid, Texasetes
Texasetes
Texasetes is a genus of ankylosaurian dinosaur from the late Lower Cretaceous of North America. This poorly known genus has been recovered from the Paw Paw Formation near Haslet, Tarrant County Texas, which has also produced the nodosaurid ankylosaur Pawpawsaurus...

 pleurohalio
(Coombs, 1995), which may prove to be a senior synonym of Pawpawsaurus. This is the only nodosaurid known to have possessed the bony eyelids commonly found in ankylosaurids. The skull of Pawpawsaurus bears some notable similarities to that of Silvisaurus
Silvisaurus
Silvisaurus, from the Latin silva "woodland" and Greek saurus "lizard", is a nodosaurid ankylosaur from the middle Cretaceous of Kansas.-Discovery and species:...

, such as the presence of teeth in the 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....

 and the restriction of the osseous secondary palate
Secondary palate
The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates.In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medially and their mutual fusion in the midline...

 to the rostral portion of the palatal region. Based on the dimensions of the skull, Pawpawsaurus is believed to have been approximately 4.5 meters in length. Vickaryous et al. (2004) have stated that "Sauropelta
Sauropelta
Sauropelta is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species has been named although others may have existed. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of...

 edwardsorum
, Silvisaurus
Silvisaurus
Silvisaurus, from the Latin silva "woodland" and Greek saurus "lizard", is a nodosaurid ankylosaur from the middle Cretaceous of Kansas.-Discovery and species:...

 condrayi
, and Pawpawsaurus campbelli form a basal polytomy
Polytomy
A polytomy , meaning many temporal based branches, is a section of a phylogeny in which the evolutionary relationships can not be fully resolved to dichotomies. In a phylogenetic tree, a polytomy is represented as a node which has more than two immediate descending branches...

 nested deep to Cedarpelta
Cedarpelta
Cedarpelta is an extinct genus of basal ankylosaurid ankylosaur, based on material recovered from the Lower Cretaceous of North America. The skull lacks extensive cranial ornamentation, a trait which has been interpreted as plesiomorphic for ankylosaurs....

."

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