THE MESOZOIC ERA: Beasts of Land and Sea
Mesozoic strata of Mississippi
The northern and eastern portions of Mississippi are home to outcrops of Late Cretaceous chalk and sands that were deposited in the shallow sea known as the Mississippi Embayment, approximately 66 million years ago. The embayment included much of present day Mississippi and extended north into what is now southern Tennessee. The embayment remainded underwater from the early Cretaceous through the Paleogene period, a duration of approximately 122 million years.
As such, most of the fossils we find in this portion of the state are marine creatures such as oysters and clams (bivalves), snails (gastropods), urchins (echinoderms), fish, shark, mosasaur (aquatic reptiles), and other sea creatures.
In the "Cretaceous Vertebrates" section you will be able to see 3-D scans of three parts of Mosasaurus hoffmanii: the left maxilla (upper jaw), the left pterygoid (internal jaw), and the left scapula (shoulder blade). The link you see will take you to an external site called Sketchfab.
The placement of shorelines change as sea level rises and falls. This map shows how the coastline of the US Southeast has changed from the Cretaceous Period through the Paleocene/Eocene epoch. The Mississippi Embayment, responsible for creating the chalk that contains many of the fossils we find in Oktibbeha County, is bound by the blue dashed line.
CRETACEOUS SNAILS (Gastropods)
Pterocella sp. (Meek 1864) Snail Fossil
Pugnellus densatus (Conrad 1860) Sea Snail Fossil
Anchura abrupta (Conrad 1860) Sea Snail Fossil
Anchura calcais (Conrad 1860) Sea Snail Fossil
Seminola crassa (Wade 1917) Sea Snail Fossil
Bullopsis cretacea (Conrad 1858) Sea Snail Fossil
Conus sp. (Linnaeus 1758) Snail Steinkern Fossil (internal mold)
Hercorhynchus tippanus (Conrad 1860) Sea Snail Fossil
Ornopsis sp. (Wade 1916) Sea Snail Fossil
Lunatia sp. (Gray 1847) Snail Steinkern Fossil (internal mold)
Gyrodes sp. (Conrad 1860) Snail Steinkern Fossil (internal mold)
Gyrodes major (Wade 1926) Sea Snail Fossil
Gyrodes abyssina (Conrad 1860) Sea Snail Fossil
Tympanotonus bindodosus (Klein 1817) Sea Snail Fossil
Pugnellus densatus (Conrad 1860) Snail Fossil
Pyropsis septemlirata (Gabb 1860) Sea Snail Fossil
Pyropsis proxima (Wade 1926) Sea Snail Fossil
Fusimilis proxima (Wade 1926) Sea Snail Fossil
Turritella sp. (Lamarck 1799) Snail Steinkern
Turritella vertebroides (Morton 1834) Sea Snail Fossil
Rostellites angularis (G. Conrad 1855) Snail Steinkern Fossil
CRETACEOUS OYSTERS and CLAMS (Bivalves)
Biradiolites sp. (d'Orbigny 1850) Rudist clam left/right valves
Anomia argentaria (Morton 1833) Single right and left valves
Paranomia scabra (Morton) right/left valve
Veniella? sp. (Stoliczka 1870) Internal mold both valves
Veniella cf. conradi (Morton 1833) Right/left valves of clam
Gervillioposis ensiformis (Conrad 1858) Single clam valve
Cardium? sp. (Linnaeus 1758) Internal mold both valves
Cardium stantoni (Wade 1926) R/L valves of clam
Cardium eufelense (Conrad 1860) Single clam valve
Cucullaea vulgaris (Morton 1830) Clam shells in matrix
Cucullaea vulgaris (Morton 1830) Ark clam right/left valve
Cucullaea vulgaris (Morton 1830) Ark clam interior view
Agerostrea falcata (Sowerby 1836) Interior and exterior views of left valve
Glycymeris microsulci (Wade 1926) Clam valves
Exogyra costata (Say 1871) Oyster right/left valve
Pycnodonte convexa (Say 1820) Oyster internal and external view of left valve
Pycnodonte vesicularis (Lamarck 1801) Oyster left valve
Pycnodonte convexa (Say 1820) Articulated right/left valve
Exogyra cancellata (Stephenson 1914) Oyster left valve - interior and exterior
Exogyra costata (Say 1971) Oyster left valve - interior and exterior
Exogyra ponderosa erraticostata (Stephenson) Oyster left/right valve
Pycnodonte mutabilis (Morton 1828) Left valve - interior and exterior
Pycnodonte cf. vesicularis (Campbell & Engel 1963) Oytster left valve - interior and exterior
Inoceramus sp. (Sowerby 1814) R/L valves of clam in matrix
Inoceramus sp. (Sowerby 1814) R/L valves of clam
Pterotrigonia aff. thoracica (van Hoepen 1929) Single Clam valve
Nucula percrassa (Conrad 1858) Single valves of clam
Ostreidae (Rafinesque 1815) Oyster small right and left valves
Striostrea plumosa (Morton) Oyster riight/left valve
Chlamys sp. (Roding 1798) Scallop valve in matrix
Pecten quinquecostatus (Brongniart 1822) Scallop shells
Plicatula aff. urticosa? (Morton 1833) Rght/left valves with internal molds
Biradiolites canaliculatus (d'Orbigny 1850) Rudist clam left valve
Paranomia scabra (Morton) right/left valve
Rudist coral - Partial left valve of giant rudist clam
Cyprimeria sp. (Conrad 1864) Single clam valve in matrix
Ostrea dliuviana (Linnaeus 1767) Oyster right/left valve
CRETACEOUS CEPHALOPODS
Belemnites sp. (Lamarck 1799) Squid pen - internal shell
Belemnitella americana (Morton 1830) Squid pen fossil
Eutrephosceras dekayi (Morton 1834) Coiled Cephalopod
Baculites sp. (Lamarck 1799) Straight-shelled ammonite
Baculites tippaensis (Conrad 1858) Straight-shelled ammonite
Baculites carinatus (Morton 1834) Straight-shelled ammonite
Mortoniceras aff. M. texanum (Roemer 1852) Ammonite
Mortoniceras sp. (Meek 1876) Coiled Ammonite
Mortoniceras sp. (Meek 1876) Coiled Ammonite
Mortoniceras aff. M. texanum (Roemer 1852) Ammonite
Eutrephoceras dekayi - Nautiloid
CRETACEOUS MISCELLANEOUS TAXA
Microbacia hilgardia (Stephenson) Coral head fossil
Hamulus squamosus var. mississippiensis (Stephenson, 1923) Tube worm fossils
Cadulus sp. (Philippi 1844) Scaphopod shell
Terebratulina sp. (d'Orbigny 1847) Articulate brachipod fossil
Entobia cretacea (Portlock 1843) Trace fossil of sponge borings in oyster
Cliona sp. (Grant 1826) Sponge fossil
Avitelmessus grapsoideus (Rathbun 1923) Crab body fossil
Amber - Fossilized tree sap
Crab Body Fossil in matrix
CRETACEOUS VERTEBRATES
Enchodus petrosus (Cope 1874) Fish tooth
Ischyrhiza mira (Leidy 1856) Sawfish rostral spine
Hadrosaurus sp. (Leidy 1858) Hadrosaur tail partial foot and partial femur
Bothremys? barberi (Leidy 1865) complete carapace
Mosasaurus aff. hoffmanii (Mantell 1829) Mosasaur quadrate
Mosasaurus sp. (Conybeare 1822) Small quadrate and jaw fragments
Tylosaur jaw Fragment
Dallasaurus? turneri (Bell and Polcyn 2005) Small Mosasaur vertebrae
Cylindracanthus ornatus (Leidy 1865) Ray finned Fish rostrum
Scapanorhynchus raphiodon texanus (Agassiz 1843) Goblin Shark Teeth
Cretelamna appendiculata (Agassiz 1835) Shark tooth
Squalicorax prisnodontus kaupi (Agassiz 1835) Shark tooth
Unidentified Fish Scales - Fossil poop
Anomoedus sp. (Forir 1887) Fish tooth plate
Bony fish fossil - articulated
3D Models of parts of Mosasaur hoffmanii (DSM 10716) can be viewed here. This will take you to an external site called "Sketchfab".
Left Maxilla (click here) - this is the upper, left jaw of the Mosasaur, and was the first piece of the specimen to be found in the outcrop.
Left Pterygoid (click here) - because the Mosasaur could not chew its prey, it had specialized, internal jaws that helped it to move the prey into its mouth and down its throat.
Left Scapula (click here)- this shoulder blade shows clear evidence that it was scavenged by a shark called Squalicorax. The grooves left behind by the shark's teeth are visible on both sides of the scapula.
Individual tooth (click here)- this tooth was from the right maxilla.
Single vertebra (click here)- this shows one of the many vertebra that were collected with this Mosasaur specimen.
