Texas Cretaceous Dinosaurs
Central Hill Country and Prairies and Lakes Areas
Cretaceous Period
Central Hill Country and Prairies and Lakes Areas
The earliest Cretaceous dinosaurs are found in the Lower Cretaceous Twin Mountain, Glen Rose and Paluxy formations that contain two main localities, Proctor Lake in Comanche County and Doss Roach in Parker County. During the Middle Cretaceous dinosaur fossils are not found due to the transgression of a shallow sea in Texas forming the Western Interior Seaway that extended from the Gulf of Mexico in the south to the Arctic Ocean in the north. Marine vertebrates have been found in these shallow marine sediments in the Central Hill Country and Parries and Lakes areas of Texas. Toward Late Cretaceous during a regression of the shallow sea, favorable dinosaur habitats again returned. Strandline, beach deposits are represented by the Paw Paw and Woodbine formations where dinosaur fossils have be found in north Texas. Other Texas formations representing marine conditions in the Interior Seaway, are the Austin Caulk, Taylor Marl and Eagleford Formation, that have been the source of marine vertebrates such as Mosasaurus and Plesiosaurs.
Dinosaurs and Associated Reptiles
Central Hill Country and Prairies and Lakes Areas
Acrocanthosaurus was among the largest carnivorous theropods ever to exist. The longest known individual measured 38 ft (11.5 m) from snout to tail tip and weighed an estimated 2.65 tons (2400 kg). Its skull alone was 4.3 ft (1.3 m) in length. Serrated teeth lined each side of the upper jaw; it had powerful front forelimbs and sharp claws. The most notable feature of Acrocanthosaurus was its row of tall neural spines, located on the vertebrae of the neck, back, hips and upper tail, which could be more than 2.5 times the height of the vertebrae from which they extended. There was no prominent crest on the lacrimal bone in front of the eye as on the Allosaurus. As with so many of the large carnivorous dinosaurs, it is thought that it may have been a scavenger rather than a predator. Track ways believed to be from Acrocanthosaurus have been found in eight Texas counties (Kinney, Bandera, Kendal, Somervell, Burnet, Travis, McLennan and Lamar). A majority of the trackways are in the Glen Rose Formation. A skull and some bones have been found near Weatherford, Texas in Mc Curtain County in the Trinity Group, Twin Mountains Formation (equivalent to the lower Antlers Formation).
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| Acrocanthosaurus Skull | Acrocanthosaurus |
Azhdarichiidae is a family of pterosaurs known primarily from the late Cretaceous Period, and which included some of the largest known flying animals of all time. They are characterized by their long legs and extremely long necks, made up of elongated neck vertebrae which are round in cross section. Azhdarichiidae had wingspans exceeding 32 ft (9.8 m)and the biggest ones were as tall as a giraffe. Most species are still known mainly from their distinctive neck bones and not much else. Azhdarichiidae are also distinguished by their relatively large heads and long, spear-like jaws. It had been suggested they were skimmers, but further research has cast doubt on this idea, demonstrating that they lacked the necessary adaptations for a skim-feeding lifestyle, and that they may have led a more terrestrial stalker existence similar to modern storks and ground hornbills. Only the humerus of an Azhdarichiidae was found in the Glen Rose Formation.
Azhdarichiidae
Coloborhynchus was a pterosaurs found in the Paw Paw Formation in Tarrant County, Texas. The only evidence of this animal comes from a well preserved top crested snout, which is long and toothed. The adult is estimated to have a wing span of 6 ft ( 1.8 m) and a length from the snout to end of the tail of 5 ft ( 1.5 m).
Deinonychus, a bird-like theropod dinosaurs, could reach 11.1 ft (3.4 m), with a maximum skull length of 1.4 ft (0.4 m), a hip height of 2.9 ft (0.87 m), a maximum weight of 161 lb (73 k). Its skull had powerful jaws lined with around 60 curved, blade-like teeth. Deinonychus was a lightly built, fast-moving, agile, carnivorous, bipedal dinosaur; it hunted in groups and lived throughout the Cretaceous Period. It had four-toed feet; the second toe had a 0.4 ft (0.13 m) sickle-like claw, and the other toes had smaller claws. Therefore, because of its long second toe, its name means "Terrible Claw". They are often called "raptors. Evidence from 6 new basal dromaeosaurid specimens found in 2001 and 2002, in the Lower Cretaceous of China, suggests that the Dromaeosauridae, including Deinonychus, was a feathered animal. It had feathered forelimbs and feet that closely resembled Archaeopteryx in flight apparatus. Deinonychus was found in the Trinity Group (antlers Formation) of north Texas.
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| Deinonychus Skull and Fore Arm | Deinonychus Killing Claw on Hind Foot |
Deinonychus
Hypsilophodont skeletons have been found as single adults, or as clusters of small adults. Flocks of young and adults lived around the Proctor Lake, Texas area. The only other fossils found at Proctor Lake with the Hypsilophodonts are a few scraps of crocodile and one tooth of a predator dinosaur like Deinonychus. Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 3.3 to 6.6 feet long (1.0 to 2.0 meters).
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| Hypsilophodont Skeleton | Hypsilophodont |
Mosasaur (mosasauroid) means "lizard of the Meuse River"; mosasaurs were not dinosaurs, but lepidosaurs, carnivorous, air-breathing marine reptiles with overlapping scales. They were related to snakes and monitor lizards. Except for the basal mosasaurs, they were a carnivorous, aquatic lizard that resembling a flippered crocodile, with elongated heavy jaws. Their legs and feet are modified into hydrofoil-like flippers, with the forelimbs larger than the hindlimbs and a long tail completed its serpentine body. Mosasaurs were powerful swimmers, adapted to living in shallow seas. Six different genera of mosasaurs have been identified in upper Cretaceous marine sediments of Texas. The mosasaurs varied from less than 3 feet to almost 50 feet ( 0.9 to 15.2 m) long.
Dallasaurus is considered to be a basal mosasaur based upon two partial skeletons recovered from the Arcadia Park Shale in Dallas County. It was a small semi-aquatic lizard capable of terrestrial and aquatic locomotion like amphibians (plesiopedal mosasaurs)
Dallasaurus
Globidens was a marine mosasaur, approximately 20 ft (6.1 m.) in length with the skull measuring about 1.6 ft (0.5 m). In appearance it was very much like other mosasaurs (streamlined body with flippers, a laterally flattened tail and powerful jaws). Most mosasaurs had sharp teeth; however the teeth of Globidens were different from other mosasaurs, as they were globular for crushing armored prey. Globidens was found in the Upper Cretaceous, Wolfe City or Lower Marl Member of the Taylor Formation.
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| Globidens Jaw | Globidens |
Russellosaurus small, lightly built mosasaur that was a semi-aquatic lizard measureing less than a meter in length. It was described from a skull discovered in an exposure of the Arcadia Park Shale (lower at Cedar Hill, Dallas County. Along with Dallasaurus, is one of the two oldest mosasaurs currently known from North America.
Tylosaurus was among the largest of all the mosasaurs, reaching maximum lengths of 49 (15.0 m) or more.. A distinguishing characteristic of Tylosaurus is its elongated, cylindrical snout from which it takes its name and which may have been used to ram and stun prey and also in intraspecific combat. The Texas specimen was about 31 ft (9.6m) long and had a 5 ft (1.5 m) long skull It was discovered in Waco, Texas in the Arcadia Park Formation. Tylosaurus has been characterized as a fierce carnivore, often larger than a Tyrannosaurus rex. (Tyrannosaurus rex grew to more than 40 ft (12.2 m) long with a skull 5 ft (1.5 m) long, while Tylosaurus proriger often grew to more than 45 ft (13.7 m) long with a skull 6 ft (1.8 m) long.
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| Tylosaurus Skull | Tylosaurus |
Mosasaurus was a 30 ft (9.1m) long mosasaurs which had a tail of about 12 ft (3.7 m). the Onion Creek mosasaur. The Texas specimen had a head of 4.7 ft (1.4 m) long, and the jaws, when fully opened, had a gape of about 3 ft (0.9 m). It was among the last Upper Cretaceous mosasaur genera, and among the largest. It was found in the Austin Chalk at Onion Creek, Texas (just south of Austin).
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| Mosasaurus Skeleton | Mosasaurus |
Nodosauridae the second of the three families of ankylosaurs found in the Early and Late Cretaceous of Texas. They are described as medium-sized to large, heavily-built quadrupedal herbivorous dinosaurs with short legs and neck, being 6 to 25 ft (1.8 to 7.6 m) long. They are set apart from the other families because they have spines on the shoulders and neck that protrude outwards. They have rows of osteoderms (a type of armour) on the dorsolateral surfaces of the body. They do not have a club on their tail, unlike the ankylosaurids.
Pawpawsaurus was a large Nodosauridae, approximately 15 to 20 ft (4.6 to 6.1 m) and 6 feet (1.8 m) high and weighing 2 tons (1,814 kg). It was found in the Late Cretaceous Paw Paw Formation in Tarrant County (north of Fort Worth), Texas.
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| Pawpawsaurus Skull | Pawpawsaurus |
Texasetes, being a similar Nodosauridae to Pawpawsaurus, is estimated to have been 8 to 10 ft (2.4 to 3.0 m) in length. It was also found in the Late Cretaceous Paw Paw Formation in Tarrant County (near Haslet), Texas.
Nodosauridae, unnamed nodosaurid material was found in the Woodbine Formation, and includes a skeleton of a baby that is believed to have fallen in the shallow sea. The bones show evidence of gnawing by scavengers and had a growth of oyster shells attached.
Pachycheilosuchus was a small crocodyliforms about 2 to 2.5 feet long (0.6 to 0.7 m). It had a shield of armor on the neck formed by the fusion of six individual scales. The specimen was found in the Glen Rose Formation in Erath County near Stephenville, Texas, representing shallow, protected, nearshore brackish water setting.
Pachycheilosuchus
Paluxysaurus was a giraffe-necked, enormous, four-footed herbivorous, basal titanosauriform sauropod dinosaur of the brachiosaurid lineage It was 30 to 60 feet (9.1 to 18.2 m) long and weighed between 20 and 45 tons (18,144 to 40,824 kg). It lived on the low coastal plain and mudflats bordering a shallow sea during the Early Cretaceous. Previously it was referred to Pleurocoelus, may be the same animal as Astrodon. It has been the state dinosaur of Texas since 1997. It has been found in the Twin Mountains Formation in Hood and Wise counties along with what are considered its tracks in the Glen Rose Formation exposed in the Paluxy and Medina rivers in Texas.
Paluxysaurus
Platypterygius was an ichthyosaur, an air-breathing and possibly omnivorous marine reptile. It had a streamlined body with a long, pointed snout and a powerful finned tail that resembled dolphins. It reached a length of about 20 feet (6.1 m). Specimens have been found in the Lower Cretaceous Grayson Formation in Tarrant County, Texas.
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| Platypterygius Skull Cast | Platypterygius |
Plesiosaurs have traditionally been divided into two major sub-groups; the long-necked, small headed "elasmosaurs" and the short-necked, larger headed "pliosaurids." For a time, this was convenient for most purposes, but it has become a somewhat arbitrary method of dividing the group since some of the so-called "pliosaurids" of the Late Cretaceous may be more closely related to the elasmosaurs. Plesiosaurs ranged in size from about 8 to 46 ft (2.4 to 14.0 m). As larger forms evolved, the necks of the long-necked forms tended to get even longer, whereas in the short-necked forms the skulls increased in length. Both types had broad, flat, apparently inflexible bodies. The Plesiosaurs were carnivorous aquatic (mostly marine) reptiles with a broad body and a short tail. They retained their ancestral two pairs of limbs, which evolved into large flippers. They were relatively slow swimmers, but because of their large flippers, they had exceptional maneuverability. They inhabitant the Interior Seaway and many specimens have been found in the marine Cretaceous of Texas.
Brachauchenius was a carnivorous short-necked Plesiosaurs (pelycosaurs) that grew to around 0 ft (10.0 m) in length. The one found near Austin, Texas in the Eagle Ford formation on Bouldin Creek had a skull length of 2.6 ft (0.8 m); the larger ones found in Kansas had skull lengths of 1.5 meters ( 5 feet) Long with an estimated weight of 19-20 tons (17,237 to 18,144 kg).
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| Brachauchenius Skull | Brachauchenius |
Ceraunosaurus was a short-necked big-head Plesiosaur that varied from 9.8 to 39.4 ft (3.0 to 12.0 m). The large skull had a heavy and elongated snout. Its teeth were conical with numerous vertical ridges. It has four large paddle-like flippers that enable it to achieve high swimming speeds. The Texas specimen, on the small side of the size range, was found the Lake Waco Formation, part of the Lower Eagleford Group, at the old Lake Waco Dam, west of Waco, McLennan County, Texas
Ceraunosaurus
Libonectes was a 23-47 ft (7.0 to 14.3 m) long-necked Plesiosaurs that has a compact body with a short tail and four large muscular large flippers. Its small skull had long, forward-facing teeth for catching prey. The long neck plesiosaurs were once believed to have been able to raise their neck and head high above the surface of the water. However, the base of the neck has been found to have been too stiff for their necks to be used in this manner. As such, the neck could only moves slightly laterally (side to side) and up-down. Texas specimen was found in the Britton Formation of the Eagle Ford Group (Upper Cretaceous), near Cedar Hill, Dallas County, Texas
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| Libonectes Skull | Libonectes |
Trinacromerum was a Late Cretaceous short-necked Plesiosaurs It was 10 feet (3.0 m) long. Its teeth show it fed on small fish. The four long flippers of Trinacromerum enabled it to achieve high swimming speeds. The Texas specimen was found in the Taylor Marl in McLennan County, Texas.
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| Trinacromerum Shull | Flipper |
Trinacromerum
Protohadros, a duckbilled herbivore dinosaur, is intermediate in morphology between the iguanodonts and the other hadrosaurids. Protohadros reached 20 ft (6.1 m) in length and had many hadrosaur-like features. It had a large, deep set of jaws, and the snout was turned down at the front, which suggests a habit of grazing on low-growing plants, rather than browsing from bushes. It is the one of the oldest and most primitive named hadrosaurids. It was found in the late Cretaceous Woodbine Formation, Flower Mound, Denton County, Texas.
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| Protohadros Shull | Protohadros |
Pterosauria were flying reptiles of the order Pterosauria. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the legs to a dramatically lengthened fourth finger. The Texas specimen was found in the Late Cretaceous Antlers Formation in North Texas.
Pterosauria
Ricardoestesia cf. gilmorei and R. isosceles, is a medium sized (~0.11 tons 100 kg), roughly 6.5 ft (2.0 m) long, carnivorous theropod dinosaur from the late Cretaceous Period. It is known from a single pair of lower jaw bones and a large number of isolated teeth. The jaws are slender and rather long but the teeth are small and finely serrated. Ricardoestesia was a raptor and it has been suggested that it was a fish eater, like a heron. Teeth found in the Woodbine Formation in north Texas has been tentatively identified as Ricardoestesia.
Ricardoestesia
Tenontosaurus was a medium - to large-sized, ornithopod, herbivore dinosaur. It was about 22 to 27 feet (6.5 to 8.2 m) long and 7 ft (2.2 m) high, with a mass of somewhere between 1 and 2 tons (907 to 1,814kg. Its tail was unusually long with ossified tendons that reinforced the tail vertebrae providing balance for its bipedal stance, however, it is believed to have walked on four feet most of the time . It is a primitive iguanodont found in the late early Cretaceous Twin Mountains Formation in Parker County, Texas (Doss Ranch) and younger Trinity Group (Glen Rose and Paluxy Formations) of Texas.
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| Tenontosaurus Skull | Tenontosaurus |
Woodbineosuchus was a narrow snouted, fish-eating goniopholid (Crocodylia Order). It was semi-aquatic, ranging from 6.5 to 13.1 ft (2.0 to 4.0 m) in length, and would have had a very similar lifestyle to the American alligator or Nile crocodile. It was found in the Woodbine Formation of north Texas.
Woodbineosuchus
Texas Dinosaurs Post Triassic Period Triassic Period Jurassic Period