The New Mexico Fossil Record
Fossils are abundant in the state of New Mexico. The history of life is recorded in the fossil record through geologic time. The geologic time scale is divided into eras: The Precambrian, Paleozoic, Mesozoic and Cenozoic.
Precambrian Era
The Precambrian spans most of the earth’s history. For over a billion years the earth was devoid of life in the Precambrian. Then life arose. The earliest life forms were microscopic bacteria they appeared almost 3.5 billion years ago. No Precambrian fossils are known from New Mexico.
Paleozoic Era
Cambrian Period
Fossils from the Cambrian Period in New Mexico include mostly brachiopods and trilobites.
Ordovician Period
Ordovician fossils from New Mexico are mostly brachiopods and nautiloids.
Silurian Period
New Mexico’s Silurian fossils consist of tabulate corals, brachiopods, pelecypods, ostracods and gastropods.
Devonian Period
Devonian fossils from New Mexico include rugose and tabulate corals, bryozoa, brachiopods, trilobites, ammonoids, nautiloids, pelecypods and gastropods.
Carboniferous Period
The Carboniferous Period is divided into the Mississippian and Pennsylvanian epochs.
Mississippian Epoch
Fossils from the Mississippian epoch in New Mexico consist of brachiopods, trilobites, gastropods, foraminiferids, ammonoids, nautiloids, conodonts, rugose corals, tabulate corals, bryozoa, crinoids, and blastoids.
Pennsylvanian Epoch
Pennsylvanian fossils in New Mexico include foraminiferids, bryozoa, rugose and tabulate corals, brachiopods, echinoids, pelecypods, gastropods, ammonoids, nautiloids, trilobites, shark teeth, bony fish scales, scaphopods, plant fossils, insects, and eurypterids.
Permian Period
The Permian Period was a time before the appearance of the dinosaurs. Strange and bizarre creatures inhabited what is now New Mexico. Some of these included the amphibian Eryops, the reptiles Ophiacodon and Sphenacodon, the sail-backed reptile Dimetrodon and the reptile Limnoscelis. It was also a time when great reef complexes covered southern New Mexico.
Mesozoic Era
Triassic Period
The first mammals, dinosaurs, crocodiles, and turtles all appeared in the Triassic Period. Most of the sinapsids or mammal-like reptiles became extinct, along with ninety percent of life on earth, in the preceding Permian period at the close of the Paleozoic Era. Therefore this was a time of replenishment of life. Many strange and wonderful creatures inhabited the Triassic landscape. What was to become the state of New Mexico 215 million years later, was then a lush environment with numerous rivers and lakes. Crocodile-like reptiles called phytosaurs occupied an ecosystem that also contained bizarre armored herbivorous reptiles termed aetosaurs, metoposaurs (large headed amphibians), a large carnivorous thecodont called Postosuchus, the small dinosaur Coelophysis, the small enigmatic armored reptile called Vancleavea, several types of fish including a lungfish, a freshwater pelecypod named Unio, many ferns, conifers, and cycads. New Mexico is well known for its Triassic rocks and the important fossil assemblages they contain.
Jurassic Period
Dinosaurs known from the Morrison Formation in New Mexico include: Camarasaurus, the families Diplodocidae including Diplodocus, Allosauridae including Allosaurus, Stegosaurus, Apatosaurus, Camptosaurus, Seismosaurus, Theropoda, Sauropoda, and Ornithopoda (Foster, 2003, p. 79-80). Petrified wood, stromatolites and dinosaur bone fragments are known from the Morrison in east-central New Mexico. Dinosaur fossils collected from this area that have no member information include: sauropod caudal vertebrae and phalanx, ornithopod cervical vertebra, Allosaurus vertebrae, and aStegosaurus vertebral centrum (Lucas et al., 1985, p. 235-236). In addition, a femur and two tibial fragments of a small theropod were collected from the Morrison in Quay County, New Mexico (Hunt and Lucas, 2006, p. 115-118). Stromatolites have been reported from the Morrison in the Dry Cimarron Valley in Union County (Neuhauser et al., 1987, p. 153-159).
Cretaceous Period
In the 1920s, the famous fossil hunter Charles Sternberg collected dinosaurs from the Fruitland and Kirtland formations in the San Juan basin. Pentaceratops, a ceratopsian dinosaur found only in New Mexico, was one of the many fossils collected from these formations by Sternberg. Other dinosaurs from New Mexico include the ankylosaur Nodocephalosaurus, the hadrosaurs Parasaurolophus and Kritosaurus, the sauropod Alamosaurus, the tyrannosaur Bistahieversor sealeyi, coelurosaurs and the pachycephalosaur Spaerotholus goodwini. Crocodile and turtle fossils are also abundant in the Fruitland and Kirtland formations. Important new dinosaurs from an earlier age have been discovered in western New Mexico in the Moreno Hill Formation. Zuniceratops, a ceratopsian, is one of these dinosaurs. A few partial mosasaurs, seagoing, serpent-like reptiles, have been discovered in the state. Many dinosaur footprints have also been found in New Mexico. William Cobban discovered and named many new ammonites from New Mexico.
Cenozoic Era
Paleogene Period
Paleocene Epoch
The Paleocene is the beginning of the age of mammals. It is a period of time spanning about 65 to 59 million years ago and, along with the preceding Cretaceous Period, delineates the boundary between the Mesozoic and Cenozoic eras. It also marks the beginning of the Tertiary Period. The dinosaurs, now extinct, have left their niches vacant. The mammals, who were living in the shadow of the dinosaurs, now occupy previously dinosaur dominated habitats. This acted as a catalyst for mammalian evolution. Mammals, who reached no larger than a dog in size, flourished and diversified in the Paleocene Epoch. The New Mexico Paleocene is used as the international standard for Paleocene mammals. The Torrejoneon and Puercan land mammal ages were named after Torrejon Wash and The Rio Puerco respectively, both in New Mexico. The Nacimiento Formation has produced many important mammal remains. David Baldwin collected in this formation in New Mexico for E. D. Cope in the late 1800s. Mammals that occur in this formation, include Deltatherium, Pantolambda, Taeniolabis (all segregated into faunal zones bearing their names), Periptychus, Psittacotherium, Mioclaenus,Promioclaenus, Mixodectes, Arctocyon, Tetraclaenodon, and others. Turtle and crocodile fossils are also abundant in this formation.
Eocene Epoch
The classic beds of the Eocene San Jose formation are well known for the mammals they contain including the Coryphodon quarry, the first horse calledHyracotherium, the small mammal Meniscotherium and the giant, flightless bird named Diatryma. In the Eocene, mammals were taking on a more modern appearance. In 1874 E. D. Cope collected in this formation in New Mexico and made many new discoveries of the time. In Cope’s own words:
As soon as we picketed the horses, we began to find fossil bone! The first thing was a turtle and then Bathmodon (Coryphodon) teeth! and then everything else rare and strange till by sundown I had 20 species of Vertebrates! all of the lowest Eocene… The most important find in geology I ever made… (from Kues, 1982, p. 185).
Oligocene Epoch
Few Oligocene fossils have been found in New Mexico. These include plant fossils and possibly titanotheres, artiodactyls and creodont carnivores (Kues, 1982, p. 190).
Neogene Period
Miocene Epoch
The Miocene sediments of the Santa Fe Group in the Espanola Basin are famous for the mammal fauna they contain. The American Museum of Natural History collected from these deposits for forty field seasons. Some of these fossils can be seen on exhibit at this museum in New York. Fossils collected from the Santa Fe Group in the Espanola Basin include the rhino Teleoceras, the horses Merychippus and Pliohippus, the camels Stenomylus andRakomylus, the “dog-bear” Hemicyon, dogs, cats, tortoises, and many other animals.
Pliocene Epoch
Pliocene fossils from New Mexico include horse fossils, camel teeth and bones, giant armored armadillo-like glyptodonts, sloth claws and bones, moles fossils, mammoth fossils, mastodon fossils, giant tortoise shells and many other fossils.
Quaternary Period
Pleistocene Epoch
Fossils from the Pleistocene or more popularly known as the Ice Age, are well represented in New Mexico in cave deposits, gravel pits, etc. Blackwater Draw near Clovis, New Mexico is a famous kill site of Pleistocene mammals, notably the Columbian mammoth. A famous find from Aden crater in New Mexico, yielded a large, complete ground sloth with hair intact and its stomach still containing its last meal.
References
Foster, John R., 2003, Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A.: New Mexico Museum of Natural History and Science Bulletin No. 23, p. 1-95.
Kues, Barry S., 1982, Fossils of New Mexico, New Mexico Natural History Series, 226 p.
Lucas, Spencer G., Kietzke, Kenneth K. and Hunt, Adrian P., 1985, The Jurassic System in East-Central New Mexico: New Mexico Geological Society Guidebook, 36th Field Conference, Santa Rosa-Tucumcari Region, p. 213-242.
Neuhauser, Kenneth R., Lucas, Spencer G., De Albuquerque, J. Stephen, Louden, Robert J., Hayden, Steven N., Kietzke, Kenneth K., Oakes, Wayne and Des Marais, David, 1987, Stromatolites of the Morrison Formation (Upper Jurassic), Union County, New Mexico: A Preliminary Report: New Mexico Geological Society Guidebook, 38th Field Conference, Northeastern New Mexico, p. 153-159.