Photograph of a mammoth tooth laying on its side on a bed of gravel. The ridged grinding surface of the tooth can be seen.

Fossils of Alaska

Simple map of Alaska.

Page snapshot: Introduction to the fossils of Alaska.


Topics covered on this page: Precambrian and Paleozoic fossils; Mesozoic fossils; Mesozoic marine fossils; Triassic marine fossils; Jurassic marine fossils; Cretaceous marine fossils; Cretaceous terrestrial fossils; Cretaceous fossils of Denali National Park; Cretaceous Colville River dinosaurs; Cenozoic fossils; Paleogene fossils; Neogene fossils; Quaternary fossils; Pleistocene mummies; The woolly mammothResources.

Credits: Most of the text on this page comes from "Fossils of the Western US" by Brendan M. Anderson, Alexandra Moore, Gary Lewis, and Warren D. Allmon, chapter 3 in The Teacher-Friendly Guide to the Geology of the Western US, edited by Mark D. Lucas, Robert M. Ross, and Andrielle N. Swaby (published in 2014 by the Paleontological Research Institution; currently out of print). The book was adapted for the web by Elizabeth J. Hermsen and Jonathan R. Hendricks in 2022. Changes include formatting and revisions to the text and images. Credits for individual images are given in figure captions.

Updates: Page last updated May 26, 2022.

Image above: A mammoth tooth on the bank of the Noatak River, Noatak National Preserve, Alaska. Photo by Julia Schock, National Park Service/NPS (public domain).

Precambrian and Paleozoic fossils

Precambrian fossils

Although most of Alaska had not been assembled before the Mesozoic, the state does contain fossil-bearing rocks dating as far back as the Precambrian. The weakly metamorphosed Precambrian rocks in eastern Alaska contain stromatolites, layered, mound-shaped fossils built by cyanobacteria.

Paleozoic fossils

Carboniferous rocks found in parts of northern Alaska, including the Brooks Range, Point Hope, and Gates of the Arctic National Park, contain corals, brachiopods, gastropods, and crinoids.


Photograph of dark gray, rounded stones on a beach with white fossils corals embedded in them. The corals mainly look like elongated white streaks or lines. In one case, the coral looks like closely packed white circles.
Photograph showing a chunk of gray rock with orange-brown, raised, tube-like areas that are the remains of a fossil coral. The fossil sits on a bed of gravel.
Photograph of gray stone on a riverbank with eroded crinoid segments embedded in it. The crinoid pieces are off-white and contrast with the background color of the stone.

A piece of gravel with worn-down crinoid stem segments on the bank of the Noatak River, Noatak National Preserve, Alaska. Photo by Julia Schock, National Park Service/NPS (public domain).

Mesozoic fossils

Mesozoic marine fossils

Triassic marine reptiles

Triassic marine reptiles are rare in Alaska. An unnamed ichthyosaur from the Brooks Range in northern Alaska is similar to Shonisaurus, a genus of large Triassic ichthyosaurs from Nevada (read more about Shonisaurus at in Earth Science of the Western United States: Fossils of the Basin and Range). A fairly complete specimen of a thalattosaurid, another type of marine reptile, was found in the Keku Islands of southeastern Alaska.


Photograph of a Triassic thalattosaurid from the Keku Islands, Alaska. The specimen is a relatively complete animal with a triangular head pointed to the right. The spine forms a slight arch and the back legs look flipper-like. The tail tapers toward the left. A 5 centimeter scale is in the corner of the photo. The specimen is dark brown to black and preserved in medium-brown rock.

A thalattosaurid (Gunakadeit joseeae) from the Triassic Hound Island Volanics, Keku Islands, southeastern Alaska. The genus is named after the Gunakadeit, a sea monster in Tlingit mythology. Paleontologists consulted with the Tlingit community before using the name for the fossil. Photo source: Figure 2 from Druckenmiller et al. (2020) Scientific Reports (Creative Commons Attribution license)


Jurassic marine fossils

Jurassic marine rocks in Alaska, which are found around Iliamna Lake in southern Alaska and across the Brooks Range on the North Slope, contain abundant ammonites and bivalves.


Photograph of a dark brown rock in which the white shells of a bivalve can be seen. A ruler at the top of the image measures 18 centimeters and extends nearly the entire image width.

Bivalves (Buchia mosquensis), Jurassic Naknek Formation, Ukak River, Alaska. Photo by Chad Hults (National Park Service/NPS, public domain).


3D model of a bivalve (Pleuromya), Jurassic Tuxedni Group, Lake Clark National Park and Preserve, Alaska. Width = 4 centimeters (1.6 inches). Source: Alaska National Parks Geology on Sketchfab (Creative Common Attribution 4.0 International license).


3D model of a ammonite (Emileia constricta), Jurassic Tuxedni Group, Lake Clark National Park and Preserve, Alaska. Width = 5 centimeters (about 2 inches). Source: Alaska National Parks Geology on Sketchfab (Creative Common Attribution 4.0 International license).


Cretaceous marine fossils

Shallow marine rocks from the Cretaceous are well represented on Alaska’s Northern Coastal Plain, around Norton Sound, the Kuskokwim Mountains, the Kenai Peninsula, and Kodiak Island. The Brooks Range and other mountains arose during the Cretaceous, which led to extensive erosion and deposition of sediment in shallow marine environments and coastal swamps. Alaska’s Cretaceous marine fossils are dominated by modern groups such as gastropods and bivalves, although ammonoids are also found.


Photograph of a Cretaceous ammonoid. The ammonoid is a shell spiraling in a single plane. In it sitting on a clear plastic stand against a white background. The fossil in brown in color and some of the complex ammonoid suturing can be seen on it surface.

An ammonoid (Pacydiscus kamishakensis), Cretaceous Kaguyak Formation, Alaska. Photo National Park Service/NPS (public domain).


3D model of an ammonite (Pachydiscus hazzardi), Late Cretaceous Kaguyak Formation, Katmai National Park, Alaska. Diameter = about 50 centimeters (almost 20 inches). Source: Alaska National Parks Geology on Sketchfab (Creative Common Attribution 4.0 International license).


Cretaceous terrestrial fossils

Cretaceous fossils of Denali National Park

Alaska reached its present latitude during the Cretaceous, when the world as a whole was much warmer. Fossils of dinosaurs, dawn redwoods, ginkgoes, and other species are common in Alaskan rocks. Fossil dinosaur tracks that are about 70 million years old have been discovered in the Cantwell Formation in Denali National Park.


Plant fossils from the Late Cretaceous, Denali National Park, Alaska. Leaves labeled on the specimen include a cycad, a dawn redwood (Metasequoia), a laurel-like plant, and an ancient sycamore. Source: Denali National Park and Preserve on Sketchfab (Creative Common Attribution-NonCommercial-NoDerivs license).


Photograph of a Cretaceous fossil trackway at Denali National Park. The trackway is preserved as a series of depression in two rows on a vertical gray rock face. A young woman stands in front of the trackway, pointing upward at it. 

Fossil trackway at Denali National Park, Alaska. Photo by Nadine Reitman, GIP (National Park Service/NPS, public domain).


Photograph of a Cretaceous hadrosaur (duck-billed dinosaur) footprint at Denali National Park. The footprint is sitting on the ground and has three toes. A scale bar of about 10 centimeters sits between one of the toes (the footprint is several times longer than the scale).

Hadrosaur track at Denali National Park, Alaska. Photo by Montana Hodges, GIP (National Park Service/NPS, public domain).


Bird tracks, Late Cretaceous Cantwell Formation, Denali National Park, Alaska. Source: Denali National Park and Preserve on Sketchfab (Creative Common Attribution-NonCommercial-NoDerivs license).


Cretaceous Colville River dinosaurs

Some Late Cretaceous dinosaurs found near the Colville River on the North Slope (northern Alaska) are spectacularly well preserved, containing more than half of their original bone material. Alaskan dinosaurs included herbivorous ceratopsians (horned dinosaurs) such as Pachyrhinosaurus; Alaskacephale, a pachycephalosaur (dome-headed dinosaurs with thick skulls); hadrosaurs (duck-billed dinosaurs) like Ugrunaaluk; ankylosaurs (armored dinosaurs), such as Edmontonia, the first dinosaur discovered in Alaska. Alaska even has its own tyrannosaur, Nanuqsaurus, which was about half the length of Tyrannosaurus rex. Other carnivores included Albertosaurus and possibly Gorgosaurus. These dinosaurs lived in conifer forests where ginkgoes and angiosperms (flowering plants) also grew.


Skeleton of a Pachyrhinosaurus on display in a museum. The Pachyrhinosaurus walks on four legs, has a stout body, a large head, and a medium-length tail. A frill extends backwards and upwards from the skull and has two horns at the top pointed outward. The mouth is beak-like. A large mass of bone occurs on the front of the face.

Skeleton of the ceratopsian (horned dinosaur) Pachyrhinosaurus perotorum from the Cretaceous of the North Slope of Alaska. Specimen on display in the Perot Museum, Dallas, Texas. Source: Photo by bryan... (Wikimedia Commons, Creative Commons Attribution-ShareAlike 2.0 Generic license, image cropped and resized).


Illustration of three Pachyrhinosaurs in a Cretaceous landscape. The Pachyrhinosaurs walk on four legs, have stout bodies, and large heads. A frill extends backwards and upwards from the head and has two horns at the top pointed outward. The mouth is beak-like. Two animals are butting heads whereas one stands off to the side, watching them. Horsetails and conifers populate the landscape, and mountains rise in the background.

Reconstruction of Pachyrhinosaurus perotorum by K. Carr. Source: Fiorillo & Tykoski (2013) PLoS ONE 8(6): e65802 (Creative Commons Attribution License).


Illustration of Alaskacephale, a pacycephalosaur. The dinosaur is bipedal (runs on two legs) and has relatively short arms. The head is small with a dome-like crown. The long tail extends backwards from the body off the ground. At the bottom right is a silhouette of a man standing next to two pacycephalosaurs . The man is taller than both dinosaurs.

Reconstruction of the pachycephalosaur Alaskacephale gangloffi by Karkemish (Wikimedia Commons, Creative Commons Attribution 3.0 Unported, image resized).


Photograph of the skull of Nanuqsaurus on display in a museum in side view. Nanuqsaurus was a predatory dinosaur with a large head and pointed teeth. Most of the skull is reconstructed from smooth white material. Two chunks of bone on the front lower jaw appear to be the only pieces of bone on the specimen.

Reconstructed skull of the tyrannosaur Nanuqsaurus; bones are brown, interpreted parts of the skull are white. Specimen on display in the Perot Museum, Dallas, Texas. Photo by Jonathan Cutrer (flickr, Creative Commons Attribution 2.0 Generic license, image cropped and resized).

Cenozoic fossils

Paleogene fossils

Paleogene fossils indicate that Alaska's climate was much warmer than it is today. In addition to plants that may occur in Alaska today, like alder (Alnus), plants characteristic of warmer climates have been found. Most notable among these are palm leaves, which have been found in southeastern Alaska in sites near the Gulf of Alaska and on Kupreanof Island. The occurrence of palms in southern Alaska is consistent with the high global temperatures that occurred in the Paleocene and Eocene.


Photography of a brown rock with the segments of a fern frond preserved as impressions on its surface. The frond impressions are a darker brown than the rock matrix. A ruler measuring 15 centimeters sits on top of the specimen.

Fossil fern, Wrangell-St. Elias National Park and Preserve, Alaska. The name and age of this specimen were not identified, but it is similar to the Eocene species Dryopteris alaskana that has been reported from the region. Photo by National Park Service (public domain).


3D model of an unidentified chunk of petrified wood, Paleocene to Eocene Ketavik Formation, Katmai National Park, Alaska. Width = 14 centimeters (5.5 inches). Source: Alaska National Parks Geology on Sketchfab (Creative Common Attribution 4.0 International license).


Neogene fossils

In Alaska’s Neogene rocks, which occur mostly along the southern coast and onto the peninsula, gastropods and bivalves are the most common marine fossils.

Land plants preserved in these rocks include many familiar tree species, like willows, poplars, alders, birches, oaks, beeches, and elms. The flora also includes some types of trees native only in Eurasia today, like dawn redwood (Metasequoia), ginkgo (Ginkgo), katsura (Cercidiphyllum), and zelkova (Zelkova). 


Photograph of large gray rock on a beach with numerous white bivalve shells embedded in its surface. 

Mollusk fossils from the Miocene Narrow Cape Formation, Fossil Beach, Kodiak Island, Alaska. Photo by Arthur T. LaBar (flickr, Creative Commons Attribution-NonCommercial 2.0 Generic license, image cropped and resized).


Desmostylians

Desmostylians are a group of enigmatic Oligocene to Miocene mammals that looked like and probably lived in similar habitats to modern hippos. Desmostylians are found only around the northern edges of the Pacific Ocean. In the eastern Pacific, they are found on the West Coast of North America from the Aleutian Islands in Alaska to Mexico. The modern relatives of these animals are unknown.

Desmostylian fossils are rare in Alaska. Only two species are known, both collected from Unalaska Island in the Aleutian Islands. The older is the Oligcene species Cornwallius sookensis, which ranged all the way south to Baja California Sur, Mexico. The younger is the Miocene species Ounalashastylus tomidai, which has been found only on Unalaska Island.


Photograph of the lower jaw of a desmostylian from Unalaska Island in a display case. The jaw is elongated and has two teeth protruding from its upper surface. The teeth are flat-surfaced.

Fossil of a desmostylian (Ounalashkastylus tomidai) lower jawUnalaska, Alaska. Specimen on temporary display in the Alaska State Museum, Juneau, 2019. Photo by J. R. Hendricks (Earth@Home).


Quaternary fossils

Much of Alaska was covered in ice during the Pleistocene ice age, but some refuges did exist where terrestrial animals were able to persist. Beringia, the land bridge that allowed humans and other animals to pass into North America from Asia, was likely one of these refuges. Numerous mammal fossils can be found throughout the state. The area around Fairbanks has many Quaternary deposits that yield mammoth, mastodon, bison, and elk bones.


Photograph of the skull of a steppe bison the Pleistocene of Alaska against a black backdrop. The skull is dark brown and has large horns that curve outward and then upward. 

Skull of a steppe bison (Bison priscus), Pleistocene, Alaska. Photo by Michael Brett-Surman (Smithsonian National Museum of Natural History, public domain).


Photograph of the skull of a moose from the Pleistocene of Alaska on display in a museum. The skull is dark brown and has large, flat horns that splay outward and turn slightly upward. The horns have jagged margins.
Photograph of the skull of a horse from the Pleistocene of Alaska in a display case. The skull is elongated with high-crowned, flat-surfaced teeth. The skull is displayed with part of the lower jaw laying on its side next to the upper part of the skull, which is resting on its teeth.

Skull of a horse, Pleistocene, North Slope, Alaska. Specimen on temporary display in the Alaska State Museum, Juneau, 2019. Photo by J. R. Hendricks (Earth@Home).


Photograph of the skull of a short-faced bear from the Pleistocene of Alaska in a display case. The skull is robust with a short snout and large canine teeth.

Skull of a short-faced bear (Artodus simus), Pleistocene, Alaska. Specimen on temporary display in the Alaska State Museum, Juneau, 2019. Photo by J. R. Hendricks (Earth@Home).


Pleistocene mummies

Rarely, frozen carcasses preserving hair and skin have been found in Alaskan permafrost, although such carcasses are more frequently found in Russia. The two most famous such mummies are "Effie," a baby woolly mammoth discovered in 1948 that is over 21,000 years old, and "Blue Babe," a steppe bison discovered in 1979 that is about 36,000 years old. Both were discovered during gold mining.

In 2012, another frozen steppe bison called "Bison Bob" was discovered in a riverbank. While Bison Bob's skeleton is nearly complete, Bison Bob is not completely mummified like Blue Babe. Nevertheless, some of Bison Bob's connective tissue and hair is preserved. Bison Bob is 43,000 years old.


Mummies of Pleistocene mammals from Alaska, 2-panel image. Panel 1: Effie the baby mammoth on display in a museum. Effie's skin is preserved. Only the front of the face, the trunk, and a foreleg is preserved. Panel 2: Blue Babe, a steppe bison, on display in a glass case. Blue Babe is shown from the side and appears to be complete. The specimen is a bison with long horns that curve outward then upward. The skin is preserved and looks leather-like.

Pleistocene mummies from Alaska on display in the Museum of the North, University of Alaska, Fairbanks. Left: Cast (reproduction) of "Effie" the baby mammoth (the original specimen is held by the American Museum of Natural History in New York City). Effie (E.F.) stands for Fairbanks Exploration (a mining company). Right: Photo of "Blue Babe," a steppe bison named after Babe the Blue Ox, who was the pet of the mythical lumberjack Paul Bunyan. Credits: Photo of "Effie" by Travis (flickr, Creative Commons Attribution-NonCommercial 2.0 Generic license, image cropped and resized). Photo of "Blue Babe" by Bernt Rostad (Wikimedia Commons, Creative Commons Attribution 2.0 Generic license, image cropped and resized).


The woolly mammoth

The woolly mammoth (Mammuthus primigenius) was a Pleistocene and early Holocene elephant that coexisted with humans. Woolly mammoths lived in both Eurasia and North America; in North America, their range extended from Alaska southeast to the northeastern United States. They were one of three species of mammoths that lived in North American during the Pleistocene. The other two were the larger Columbian mammoth (Mammuthus columbi), which ranged throughout most of the lower 48 U.S. states and into Mexico, and the small pygmy mammoth (Mammuthus exilis), which was found only on the Channel Islands in southern California. 


Diagram showing the relative sizes of the three species of mammoth that are found in the Pleistocene of North America. From largest to smallest they are the Columbian mammoth, the woolly mammoth, and the pygmy mammoth.

Size comparison of the three types of mammoths found in the Pleistocene of North America. Diagram modified by a diagram by FunkMunk (Wikimedia Commons, public domain).


Woolly mammoths were similar to modern African elephants in size but had a heavy coat of fur, small ears, and a short tail to minimize heat loss. Mammoths primarily ate grasses and sedges and had flat teeth similar to those of modern elephants. 

Most woolly mammoths, along with many other megafauna, went extinct during the Quaternary extinction event as a result of climate change and exploitation by human hunters; the relative contribution of each of these factors is still disputed. The youngest woolly mammoths from the United States come from St. Paul Island (a remote volcanic island located to the southwest of mainland Alaska), where they survived until about 5600 years ago. The last known woolly mammoths in the world survived on Wrangel Island (a Russian island to the north of eastern Russia and northwest of Alaska) until about 4000 years ago. 


Photograph of a model of a woolly mammoth on display in a museum. The mammoth looks like an elephant with long, shaggy brown hair. It has long tusks that curve upward.

Model of a woolly mammoth on display at the Royal Victoria Museum, British Columbia, Canada. Photo by Thomas Quine (Wikimedia Commons, Creative Commons Attribution 2.0 Generic license, image resized).


Black and white photo of five men posting with a mammoth tusk. Two of the men are holding up the tusk, which has its base and tip resting on the ground. The man in the center holds a little girl who is standing on the apex of the arch formed by the tusk. 

The Biederman family and their friends with a mammoth tusk, Yukon River, Alaska, 1930. Photo source: National Park Service/NPS (public domain).


Photograph of a mammoth molar from the side. The molar has a flat chewing surface and the underside or roots form a diagonal surface. The tooth is brown. A ruler shows that the tooth is about 30 centimeters or 1 foot in length.

A large woolly mammoth molar, Pleistocene, Bering Land Bridge National Preserve, Alaska. This tooth was radiocarbon dated and is between 14,530 and 14,060 years old. Photo by Jeff Rasic (National Park Service/NPS, public domain).


Photograph of the shore of St. Paul Island is Alaska. The photo shows a gently sloping landscape ending in a steep cliff at the edge of the sea. The island is covered with short, yellow plants, possibly grasses.

St. Paul Island, Pribilof Islands, southwestern Alaska, June 2012. Photo by Don Henise (flickr, Creative Commons Attribution 2.0 Generic license, image resized).

Resources

Resources from the Paleontological Research Institution

Digital Atlas of Ancient Life Virtual Collection: https://www.digitalatlasofancientlife.org/vc/ (Virtual fossil collection featuring 3D models of fossil specimens sorted by group)

Digital Encyclopedia of Ancient Life: https://www.digitalatlasofancientlife.org/learn/

Earth@Home: Quick guide to common fossils: https://earthathome.org/quick-faqs/quick-guide-common-fossils/


Go to the full list of resources about fossils in the western U.S.

Go to the full list of general resources about fossils