''Appalachiosaurus'' ( ; "Appalachian lizard") is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of tyrannosaurian

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

period of what is now eastern

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. It was a basal member of the

Eutyrannosauria Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent be ...

clade meaning it was rather close in relation to the true tyrannosaurids such as ''

Tyrannosaurus ''Tyrannosaurus'' () is a genus of large theropod dinosaur. The type species ''Tyrannosaurus rex'' ( meaning 'king' in Latin), often shortened to ''T. rex'' or colloquially t-rex, is one of the best represented theropods. It lived througho ...

''. Like most theropods, it was a

biped Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' ' ...

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

. Only a juvenile skeleton has been found, representing an animal approximately long and weighing , which indicates an adult would have been significantly larger.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s of ''Appalachiosaurus'' were found in central Alabama's

Demopolis Chalk Formation The Demopolis Chalk is a geological formation in North America, within the U.S. states of Alabama, Mississippi, and Tennessee. The chalk was formed by pelagic sediments deposited along the eastern edge of the Mississippi embayment during the midd ...

. This formation dates to the middle of the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

age of the

, around 77

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

. Fossil material assigned to ''Appalachiosaurus'' is also known from the Donoho Creek and

Tar Heel Tar Heel (or Tarheel) is a nickname applied to the U.S. state of North Carolina and its people. It is also the nickname of the University of North Carolina athletic teams, students, alumni, and fans. The origins of the Tar Heel nickname trace ba ...

-Coachman formations of

North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

and

South Carolina South Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders North Carolina to the north and northeast, the Atlantic Ocean to the southeast, and Georgia (U.S. state), Georg ...

in 2007. As well as the

Ripley Formation The Ripley Formation is a geological formation in North America found in the U.S. states of Alabama, Georgia, Mississippi, Missouri, and Tennessee. The lithology is consistent throughout the layer. It consists mainly of glauconitic sandstone. It ...

in the Hannahatchee Creek in

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

Discovery and naming

The type specimen was found by

Auburn University Auburn University (AU or Auburn) is a Public university, public Land-grant university, land-grant research university in Auburn, Alabama, United States. With more than 26,800 undergraduate students, over 6,100 post-graduate students, and a tota ...

geologist David King in July 1982. This dinosaur was named after the region of the eastern

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

known as

Appalachia Appalachia ( ) is a geographic region located in the Appalachian Mountains#Regions, central and southern sections of the Appalachian Mountains in the east of North America. In the north, its boundaries stretch from the western Catskill Mountai ...

, which also gave its name to the ancient island continent where ''Appalachiosaurus'' lived. Both are named after the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

. The generic name also includes the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word ''sauros'' ("lizard"), the most common suffix used in dinosaur names. There is one known

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, ''A. montgomeriensis'', which is named after

Montgomery County Montgomery County may refer to: Australia * The former name of Montgomery Land District, Tasmania United Kingdom * The historic county of Montgomeryshire, Wales, also called County of Montgomery United States * Montgomery County, Alabama * Montg ...

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

. Both the genus and species were named in 2005 by

paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...

s Thomas Carr and Thomas Williamson.

Description

The juvenile specimen of ''Appalachiosaurus'' measures approximately long and . So far, it is only known from partial remains, including parts of the

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

and lower jaw, as well as several

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e, parts of the

pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

, and most of both legs. These remains are housed at the

McWane Science Center The McWane Science Center (formerly known as the McWane Center) is a science museum and research archive located in downtown Birmingham, Alabama, United States. The state-of-the-art hands-on science center, aquarium, and 250-seat IMAX Dome Theat ...

Birmingham, Alabama Birmingham ( ) is a city in the north central region of Alabama, United States. It is the county seat of Jefferson County, Alabama, Jefferson County. The population was 200,733 at the 2020 United States census, 2020 census, making it the List ...

. There are several open sutures between bones of the skull, indicating that the animal was definitely a juvenile. Several of its bones are crushed, but the specimen is still informative and shows many unique characteristics. Several of these have been identified in the skull and the foot claws show an unusual protrusion on the end closest to the body. A row of six low crests lines the top of the snout, similar to those of the

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

n ''

Alioramus ''Alioramus'' (; meaning 'different branch') is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. It currently contains two species. The type species, ''A. remotus'' is known from a partial skull and three foo ...

'', although most tyrannosaur species exhibit ornamentation to varying degrees on top of their snout and brows. The only remains found are from a juvenile, meaning that the size and weight of an adult is unknown. ''Appalachiosaurus'' is significantly different and more derived than another eutyrannosaur from eastern North America, ''

Dryptosaurus ''Dryptosaurus'' ( ) is a genus of eutyrannosaurian theropod dinosaur that lived on the island continent of Appalachia approximately 67-66 million years ago during the end of the Maastrichtian age of the Late Cretaceous period. ''Dryptosaurus'' ...

''.

The arms of ''Appalachiosaurus'' are poorly known. Large tyrannosaurids are characterized by proportionally small arms and hands with two functional fingers. Although some reports of a

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

are ascribed to ''Appalachiosaurus'', no arm material is actually known. Early reconstructions gave it long arms with three large fingers, but they are now thought to have been much shorter and have only two fingers. Museum mounts have been corrected accordingly, though other locations still support the former theory.

Classification

The only known specimen of ''Appalachiosaurus'' was complete enough to be included in phylogenetic analyses using

cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...

. The first was performed before the animal had even been named and found ''Appalachiosaurus'' to be a member of the

Albertosaurinae Albertosaurines, or dinosaurs of the subfamily Albertosaurinae, lived in the Late Cretaceous of United States and Canada. The subfamily was first used by Philip J. Currie, Jørn H. Hurum, and Karol Sabath as a group of tyrannosaurid dinosaurs ...

subfamily of Tyrannosauridae, which only includes ''

Albertosaurus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million yea ...

'' and ''

Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Ca ...

''.Holtz, T.R. (2004). "Tyrannosauroidea." In: Weishampel, D.A., Dodson, P., & Osmolska, H. (Eds.). ''The Dinosauria'' (2nd Edition). Berkeley: University of California Press. Pp. 111–136. The original description also included a cladistic analysis, finding ''A. montgomeriensis'' to be a basal tyrannosauroid outside of Tyrannosauridae. However, Asian tyrannosaurs, like ''Alioramus'' and ''

Alectrosaurus ''Alectrosaurus'' (; meaning "alone lizard") is a genus of Tyrannosauroidea, tyrannosauroid theropod dinosaur that lived in Asia during the Late Cretaceous period, about some 96 million years ago in what is now the Iren Dabasu Formation. It was ...

'', were excluded, as was ''

Eotyrannus ''Eotyrannus'' (meaning "dawn tyrant") is a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The re ...

'' from

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

. Earlier tyrannosaurs, such as '' Dilong'' and ''

Guanlong ''Guanlong'' (冠龍) is a genus of extinct proceratosaurid tyrannosauroid dinosaur from the Late Jurassic of China. The taxon was first described in 2006 by Xu Xing ''et al.'', who found it to represent a new taxon related to ''Tyrannosaurus' ...

'', had not been described at the time this analysis was performed. These exclusions may have a significant effect on the phylogeny. Below is a cladogram published in 2013 by Loewen ''et al.''.

Paleobiology

''Appalachiosaurus'' had a bone-crushing bite force of around 32,500 newtons, or 7,193 pounds per square inch.

Paleopathology

Two vertebrae of the tail were found to be fused together, which is possibly a result of new

bone growth Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in the ...

following some sort of minor or traumatic injury.

References