Texas Dinosaurs

Texas Dinosaurs

Three geologic periods (Triassic, Jurassic and Cretaceous) define the Age of Dinosaurs. It encompasses a period of time from about 142 million years ago to about 65 million years ago. In Texas dinosaurs are found in three main areas: Panhandle Plains, Hill Country and Prairies and Lakes and Big Bend Country. Each area also has a unique assemblage of species and together they are known as the Age of Reptiles in Texas. In discussing dinosaurs, their reptile cousins must be included because they shared in the same time period, habitat and evolutionary pressures.

The following table provides the geologic periods represented in Texas and the generally accepted age when Texas dinosaurs were present..

Area	Period	Age*	Geologic Unit
Pan Handel Area	Late Triassic	227-210 Carnian to Norian	Dockum Group Bull Canyon M. Tecovas M. Colorado City M. Camp Springs M.
Central Hill Country Area	late Early and early Late Cretaceous	115 to 99 and 99 to 93 late Aptian to Albian and Cenomanian	Woodbine Formation Paw Paw Formation Paluxy Formation Glen Rose Formation
Big Bend Area	late Late Cretaceous	83-65 Maastrichtian to Campanian	Black Peaks Formation Javelina Formation El Picacho Formation Aguja Formation San Carlos Formation Pen Formation

* Age in million years before present

Dinosaurs are divided into two main groups, the Order ornithischians (bird-hipped) and Order saurischians (lizard-hipped), both of which, based on fossil finds, appeared to arise in the Late Triassic, between 225 and 200 million years ago.

The ornithischians and saurischians were thought to evolve concurrently, the latest thought is that the saurischians evolved in the Late Triassic Period in Texas; not the ornithischians. The ornithischians evolved in the late Late Triassic only in South America, maybe. The early ornithischians were thought to have evolved into animals such as the stegosaurs of the Jurassic and the frilled and duck-billed dinosaurs of the Cretaceous, while the saurischians split into the sauropodomorphs - the long-necked browsers like Brachiosaurus - and the carnivorous theropods, like Tyrannosaurus rex. Only the theropods survive to the present as birds. Reptiles, including dinosaurs are classified in the Phylum coradata and Subphylum vertebrata. The classification of reptiles with notes (modified from Benton 2005) is presented below.

Further discussions of Texas Dinosaurs is provided by the following links.

Texas Dinosaurs Post Triassic Period Triassic Period Jurassic Period Cretaceous Period

Central Hill Country and Prairies and Lakes Areas Big Bend Country Area

* Note: These web pages concerning Texas Dinosaurs is an attempt to describe the basic geologic framework during the "Age of Dinosaurs" and bring together in one place a basic description of the major Texas Dinosaurs and Associated Reptiles of Texas.. T his includes where they were found, a photograph of the skeleton (not necessarily the Texas specimen) and an image of what it may have looked like. Most all the information is from the "world wide web" and at this time references have not been provided at this time.

CLASSIFICATION OF THE REPTILES

Series Amniota

Class Synapsida - mammal-like reptiles

Order Pelycosauria- primitive synapsids that radiated into carnivorous (ophiacodonts & sphenacodonts)

and herbivorous (edaphosaurs)forms. Dominant reptiles from late Carboniferous to mid-Permian

Family Eothyrididae

Family Caseidae

Family Varanopseidae

Family Ophiacodontidae

Family Edaphosauridae

Family Sphenacodontidae

Order Therapsida- mammal-like reptiles that arose from sphenacodonts in the mid-Permian.

An early group of primitivecarnivores (pthinosuchians) quickly gave rise to advanced

carnivorous (theriodonts) and herbivorous (dinocephaliansanomodonts) suborders.

They thrived from Permian until the late Triassic.

†Suborder Biarmosuchia – primitive Permian therapsids

†Suborder Dinocephalia – large early therapsids that flourished in the Middle Permian

†Suborder Dicynodontia– large to small therapsids with two tusks in the Permian-Traissic

†Suborder Gorgonopsia– on of the largest carnivorous therapsids in the late Permian

Suborder Cynodontia– modern therapsids and some extinct ones with dog-like teeth

†Family Procynosuchidae

†Family Galesauridae

†Family Cynognathidae

†Family Diademodontidae

†Family Chiniquodontidae

†Family Tritylodontidae

†Family Tritheledontidae

Class Sauropsida

Subclass Anapsida- captorhinids, cotylosaurs, turtles

†Family Mesosauridae

†Family Millerettidae

†Family Bolosauridae

†Family Procolophonidae

†Family Pareiasauridae

Order Testudines (Chelonia) - turtles

†Family Proganochelyidae

†Family Australochelidae

Suborder Pleurodira–side-neck turtles

Suborder Cryptodira– most living turtles and tortoises

Superfamily Baenoidea

†Family Meiolaniidae

Superfamily Chelonioidea

Superfamily Trionychoidea

Superfamily Testudinoidea

†Family Captorhinidae

†Family Protorothyrididae

Subclass Diapsida– reptiles that developed two holes (temporal fenestra) in each side of their skull

†Order Araeoscelidia– extinct small lizard-like reptiles from Devonian - Permian

†Family Weigeltisauridae

†Order Younginiformes– primitive lizard-like reptiles in Permian -Triassic

†Infraclass Ichthyosauria sedis mutabilis- marine reptiles that resembled fish and dolphins in

Triassic-Cretaceous

Infraclass Lepidosauromorpha

†Superorder Sauropterygia

Order Placodontia- pleisiosaurs, icthyosaurs, placodonts

Order Nothosauroidea

Suborder Pachypleurosauria

Suborder Nothosauria

Order Plesiosauria

Suborder Plesiosauroidea

Family Cryptoclididae

Family Cimoliasauridae

Family Polycotylidae

Family Elasmosauridae

Suborder Pliosauroidea

Family Rhomaleosauridae

Family Pliosauridae

Superorder Lepidosauria

Order Sphenodontida

Family Sphenodontidae

†Family Pleurosauridae

Order Squamata–scalled reptiles, snakes and lizards

Suborder Lacertilia (Sauria) - lizards

Infraorder Iguania- iguanas, chameleons; New World lizards

Infraorder Gekkota– includes geckos

Infraorder Amphisbaenia – legless lizards similar to earth worms

Infraorder Anguimorpha– extinct mosasaras

Infraorder Scincomorpha – some skinks

Suborder Serpentes (Ophidia) - snakes

Infraclass Archosauromorph- an Infraclass of diapsid reptiles that first appeared during the late Permian and

became common during the Triassic

†Family Trilophosauridae

†Family Rhynchosauridae

†Order Prolacertiformes- extinct reptiles related to crocodiles and alligators are surviving member of

this group

Division Archosauria - group of diapsid reptiles represented by modern birds and crocodilians.

This group also includes extinct non-avian dinosaurs, pterosaurs and relatives of crocodiles

†Family Proterosuchidae

†Family Erythrosuchidae

†Family Euparkeriidae

Subdivision Crurotarsi

†Family Phytosauridae– includes protorosaur

†Family Ornithosuchidae sedis mutabilis

†Family Stagonolepididae sedis mutabilis

†Family Rauisuchidae sedis mutabilis

†Family Poposauridae sedis mutabilis

Superorder Crocodylomorpha– crocodilians and their extinct

†Family Saltoposuchidae

†Family Sphenosuchidae

Order Crocodylia– crocodilians and their extinct relatives

†Family Protosuchidae

Division Mesoeucrocodylia

†Family Teleosauridae

†Family Metriorhynchidae

Subdivision Metasuchia

†Family Notosuchidae

†Family Sebecidae

Infradivision Neosuchia

†Family Goniopholididae

†Family Dyrosauridae

Suborder Eusuchia–living

crocodilian and some

extinct

Family Gavialidae

Family Crocodylidae

Family Alligatoridae

Subdivision Avementatarsalia

†Scleromochlus

Infradivision Ornithodira - characterized by an upright gait and an S-curved neck,

hence the name "Ornithodira" ("bird necks")

†Order Pterosauria- flying reptiles: pterodactyls, pteranodons

Suborder Rhamphorhynchoidea

Suborder Pterodactyloidea

†Lagerpeton

†Marasuchus

Superorder Dinosauria - all dinosaurs from Triassic - Cretaceous, including

bird-hipped and lizard-hipped

Order Saurischia- lizard-hipped dinosaurs from Triassic, included many

carnivores & herbivores

†Family Herrerasauridae

Suborder Theropoda- mostly bipedal forms

included diverseomnivores (coelursaurs)

and carnivores

(carnosaurs)

†Infraorder Coelophysoidea– feathered

bipedal predators dinosaurs, includes

tyrannosaurus

†Infraorder Ceratosauria - large bipedal predatory

dinosaurs

Family Ceratosauridae

Family Abelisauridae

Infraorder Tetanurae - large bipedal predatory dinosaurs

related to modern birds

†Division Carnosauria giant

predatory dinosaurs,

allosaurus

Subdivision Spinosauroidea - includes

megalosaurus

Family Megalosauridae

Family Spinosauridae

Subdivision Allosauroidea - includes

allosaurus, giganotosaurus

Family Allosauridae

Family Carcharodontosauridae

Division Coelurosauria -all feathered dinosaurs,

includes tyrannosaurus

†Family Coeluridae

Subdivision Maniraptoriformes

†Family Tyrannosauridae

†Family Ornithomimidae

Infradivision Maniraptora

†Family Alvarezsauridae

†Family Therizinosauridae

Cohort Deinonychosauria

Family Dromaeosauridae

Family Troodontidae

†Suborder Sauropodomorpha- gigantic quadrupedal sauropods

herbivor

Thecodontosaurus

Family Vulcanodontidae

Family Plateosauridae

Riojasaurus

Family Massospondylidae

Infraorder Sauropoda - larges animal to have lived on land,

brontosaurus, alamosaurus

Family Omeisauridae

Division Neosauropoda–giant herbivore quadrupedal

dinosaurs

Family Cetiosauridae

Family Diplodocidae

Subdivision Macronaria - largest dinosaurs to

have roamed the earth

Family Camarasauridae

Infradivision Titanosauriforme

Family Brachiosauridae

Cohort Somphospondyli

Family Euhelopodidae

Family Titanosaurida

†Order Ornithischia-bird-hipped later dinosaurs from Jurassic

& Cretaceous; mostly herbivorous and carnivorous

Family Pisanosauridae

Family Fabrosauridae

Suborder Thyreophora - herbivorous armored dinosaurs

Family Scelidosauridae

Infraorder Stegosauria - large quadrupedal herbivore,

stegosaurus

Infraorder Ankylosauria

Family Nodosauridae

Family Ankylosauridae

Suborder Cerapoda - armored quadrupedal dinosaurs

Infraorder Pachycephalosauria - bipedal thick skulled

dinosaurs, dracorex, stegoceras

Infraorder Ceratopsia quadrupedal herbivores with beaks

& powerful neck muscles and frill on back

of neck

Family Psittacosauridae

Family Protoceratopsidae

Family Ceratopsidae

Infraorder Ornithopoda- duck-billed dinosaurs, iguanodonts

Family Heterodontosauridae

Family Hypsilophodontidae

Family Iguanodontidae

Family Hadrosauridae

† Extinct groups

Texas Dinosaurs Post Triassic Period Triassic Period Jurassic Period

Cretaceous Period

Central Hill Country & Prairies and Lakes Areas Cretaceous Big Bend Country Area Cretaceous