The Antlers Formation is a

stratum In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as e ...

which ranges from

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the ...

through southern Oklahoma into northeastern

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

. The stratum is thick consisting of silty to sandy mudstone and fine to coarse grained

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

that is poorly to moderately sorted. The stratum is cemented with

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay part ...

and calcium carbonate. In places the sandstone may be conglomeratic or ferruginous (rich in iron oxides). Based on correlation with the

Trinity Group The Trinity Group is a group (sequence of rock strata) in the Lower Cretaceous lithostratigraphy of Texas, Arkansas, Mississippi, Louisiana and Oklahoma. It is named for the Trinity River of Texas. A stratigraphic column at the Mount Bonnell Fau ...

of Texas, the Antlers Formation is estimated to be late

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 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

-early

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 113.0 ± 1.0 Ma to 100.5 ± ...

. This age range is supported by the presence of two dinosaurs that are also known from the Cloverly Formation, '' Deinonychus'' and '' Tenontosaurus''.

Amphibians

Indeterminate frog remains. Possible indeterminate salamander remains.

Fish

References: Cifelli ''et al.'' 1999; Wedel ''et al.'' 2000, Kielan-Jarorowska and Cifelli 2001; Nydam and Cifelli 2002.

Cartilaginous fish

Ray-finned fish

Possible indeterminate amid remains. Possible indeterminate lepisosteid remains. Possible indeterminate semionotidae remains.

Mammals

Possible indeterminate deltatheroidan material. Indeterminate multituberculate remains. Indeterminate tribosphenidan remains.

Reptiles

Crurotarsans

Possible indeterminate atoposaurid remains. Possible indeterminate goniopholidid remains. Possible indeterminate pholidosaurid remains.

Lepidosaurs

Possible indeterminate scincid remains.

Ornithischians

Saurischians

Possible indeterminate bird remains are known from the formation.

Turtles

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Turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked ...

s of the Antlers Formation , - ! Genus ! Species ! Location ! Stratigraphic position ! Abundance ! Notes , - , ?'' Glyptops'' , ''Glyptops'' sp. , , , , , - , ''

Naomichelys ''Naomichelys'' is an extinct genus of helochelydrid stem turtle known from the Cretaceous (Aptian-Campanian) of North America. It is the only member of the family known to be native to North America. Distribution ''Naomichelys'' is known nume ...

'' , ''Naomichelys'' sp. , , , , , -