Justin Tweet

• Master of Science
• Researcher at National Park Service

Cuyahoga Valley National Park (CUVA) was established as Cuyahoga River National Recreation Area on December 27, 1974, to preserve and protect the Cuyahoga River Valley and its historic, scenic, natural, and recreational values. While not explicitly mentioned in the park’s mission statement, paleontological resources preserved at CUVA are neverthele...

Mammoth Cave National Park (MACA) in central Kentucky holds the longest cave system in the world, with cave passages cutting through Middle to Upper Mississippian limestones. These limestones hold records of fish assemblages, mostly dominated by chondrichthyans, that are primarily identified from isolated teeth, spines, and occasional skeletal cart...

Dr. Martin G. Lockley explored and published extensively on vertebrate ichnological resources at Glen Canyon National Recreation Area (GLCA), primarily from the shores of Lake Powell in Utah and Arizona. Since 2010, a team from the St. George Dinosaur Discovery Site, working in conjunction with GLCA and National Park Service paleontologists, has fo...

Bryce Canyon National Park Paleontological Resource Inventory

Colorado National Monument (COLM) in western Colorado was established on May 24, 1911 with the purpose of preserving, understanding, and enjoying the natural and cultural resources of the landscape, focusing on the history, erosional processes, and geology present. Although not explicitly mentioned in the monument’s purpose statement, the paleontol...

Two new ctenacanthiform sharks representing two families, Ctenacanthidae and Heslerodidae, have been identified from the Middle to Late Mississippian marine sediments from Mammoth Cave National Park, Kentucky, and two Late Mississippian marine horizons in northern Alabama. The ctenacanthid, Troglocladodus trimblei, gen. et sp. nov., is known from i...

The fossil record preserved throughout the parks, monuments, and other areas administered by the National Park Service spans at least 1.4 billion years and reveals rich and diverse paleontological resources available for scientific research and public education. Fossils documented in at least 286 different NPS areas represent important and iconic c...

George Washington Birthplace National Monument (GEWA) is a National Park Service (NPS) unit located in the Northern Neck of Virginia, situated on low bluffs overlooking the Potomac River. This small park unit, focused primarily on cultural and historical resources, may seem at first glance to be an unlikely candidate for notable paleontological res...

The history associated with the discovery, research, preservation, protection, and loss of the fossil cycadeoid locality near Minnekahta in the southern Black Hills of South Dakota-which for 35 years was designated as Fossil Cycad National Monument-has gained considerable public attention. Several publications have attempted to capture por tions of...

A focused search for ancient Mississippian Subperiod marine vertebrates during a paleontological resource inventory of Mammoth Cave National Park, Kentucky, has yielded a wealth of new fossil data, previously unrecognized at this park. To date, we have identified marine vertebrate fossils from four primary horizons at the park, two of which are the...

Theodore Roosevelt National Park (THRO) in western North Dakota comprises badlands that surround the Little Missouri River in three separate units. Established initially as a national memorial park in 1947 and redesignated as a national park with its current boundaries in 1978, THRO was founded for its connection to its amesake, the United States p...

Description of a new petalodont shark from the Middle Mississippian Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky.

In the 1960s, United States Geological Survey (USGS) geologists working in the Late Cretaceous (Maastrichtian) Harebell Formation in the Big Game Ridge area of Yellowstone National Park, Wyoming, collected the first known dinosaur fossil from this iconic park. Consisting of a single shed theropod tooth, the fossil was previously identified as a “de...

Isolated teeth of two janassid petalodonts collected from cave passages within the Middle Mississippian (Viséan) Joppa Member of the Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky represents the first record of this group of chondrichthyans from this formation. A new janassid, Strigilodus tollesonae, gen et sp. nov., is recognised...

This report represents the first comprehensive paleontological resource inventory for Wind Cave National Park, South Dakota. This is the public version of the park's paleontological resource inventory.

The lands under the jurisdiction of the National Park Service (NPS) have an extensive chondrichthyan (cartilaginous fish) fossil record that spans temporally all the eras of the Phanerozoic and geographically throughout the United States. A total of 46 NPS units have yielded fossil chondrichthyans representing 16 units with specimens from the Paleo...

A jaw fragment with a lower third molar of a small brontothere, Palaeosyops sp. cf. P. laevidens, was collected from a volcanic alluvial mudflow conglomerate from the Wapiti Formation of the Absaroka Volcanic Supergroup, on Mount Hornaday, in the northeastern section of Yellowstone National Park, Wyoming. Palaeosyops laevidens has been found in ear...

An isolated tooth of Carcharopsis wortheni was collected from the Middle Mississippian (Visean) Mexican Springs Formation of the Perdido Group at Death Valley National Park, California by USGS staff in 1963. This marks the first record of this euselachian chondrichthyan taxon for both California and Death Valley National Park and the first descript...

The data assembled for the National Park Service's Paleontology Synthesis Project (PSP) have made it feasible to analyze the geochronological scope of NPS paleontological resources. Paleontological resources have been documented for 283 NPS units and affiliated areas; 245 have confirmed in situ or reworked fossils. From this subset, the NPS record...

Abstract—Carlsbad Caverns National Park (CAVE) is located in southeastern New Mexico, southwest of Carlsbad, Eddy County. Situated in the Chihuahuan Desert, the park includes more than 120 caverns of all sizes, formed by millions of years of limestone dissolution. Best known to visitors for its cave systems with expansive rooms adorned with spectac...

A report on the paleontological resources found in Theodore Roosevelt National Park in western North Dakota including local geology, taxonomy of local fossils, fossil localities within the park, museum collections and paleontological archives of materials found in the park, a review of park paleontological research, paleontological interpretation,...

Mammoth Cave National Park (MACA) in Kentucky contains the longest known cave system in the world. Over 400 miles of passages cut through Late Mississippian sedimentary rocks representing three geologic formations. The oldest of these Late Mississippian beds is the Horse Cave Member of the upper portion of the St. Louis Formation. The St. Louis For...

The fossil record of Grand Canyon National Park is expansive from geospatial, geologic, temporal paleotaxonomic and paleoenvironmental perspectives. The fossiliferous sedimentary strata are heavily dissected throughout the park’s 4,950 square kilometers (1,904 square miles), with a 446 km (277 mile)-long canyon cut by the Colorado River reaching an...

Captions and script for my video presentation of this conference poster.

A video file containing my recorded presentation for this virtual conference poster.

Two rock surfaces (part and counterpart) in the Mesoproterozoic Dox Formation, collected and reported by Edwin D. McKee in the early 1930s, preserve a polygonal pattern of spindle-shaped, sediment-filled fractures. They are remarkably similar to microbially-mediated shrinkage cracks filled with petees sensu lato documented from other Proterozoic an...

This is a comprehensive inventory of paleontological resources in Grand Canyon-Parashant National Monument.

Belemnites (order Belemnitida) are an extinct group of coleoid cephalopods, known from the Jurassic and Cretaceous periods. We compiled detailed information on 252 occurrences of belemnites in six National Park Service (NPS) areas in Alaska. This information was based on published literature and maps, unpublished U.S. Geological Survey internal fos...

The vast taxonomic breadth of the National Park Service (NPS)'s fossil record has never been systematically examined until now. Paleontological resources have been documented within 277 NPS units and affiliated areas as of the date of submission of this publication (Summer 2020). The paleontological records of these units include fossils from dozen...

Carlsbad Caverns National Park (CAVE) is located about 20 miles southwest of Carlsbad, New Mexico. The park is situated in the northern Chihuahuan Desert, and contains more than 119 caverns of various sizes. Though CAVE is best known for several cave systems with expansive rooms adorned with spectacular speleothems, the park also preserves signific...

Executive Summary: Since Agate Springs Ranch was founded by James H. Cook in 1887, exquisite examples of transitional Miocene mammalian fauna have been found along this stretch of the Niobrara River valley. Collectively these paleontological discoveries, along with the existing archeological and historical Native American collection, were the bas...

This document is an inventory of the paleontological resources of Carlsbad Caverns National Park (CAVE), representing a combination of field work and literature synthesis. It begins with background summaries about the park and its geological, paleontological, and scientific history. It then moves into descriptions of paleontological resources incl...

Proboscideans (Mammalia, Proboscidea) are an ubiquitous part of North American vertebrate faunas throughout the Miocene, Pliocene, and Pleistocene. Here we discuss the fossil record of proboscideans found on public lands administered by the National Park Service (NPS), which is comprised of 419 units. At least 276 of these units contain some aspect...

The principal goals and objectives for the Grand Canyon National Park Centennial Paleontological Resource Inventory were to identify the scope, significance, distribution and management issues associated with the fossils of the park. Through this effort we compiled baseline paleontological resource information for park managers and staff to better...

The story that Grand Canyon tells is a spectacle of approximately two billion years of earth history (approximately one-half of the age of the earth) in its rock record, with an equally extensive paleontological component. There is no other place on Earth where the pages of Earth’s story can be read so easily by the observer to reveal such a long,...

Our planet has a rich paleontologic history of life and environments that is uniquely captured in the brilliant rocks on display at Grand Canyon National Park (GRCA). The span of the Paleozoic fossil record at GRCA encompasses over about 250 million years of snapshots of ancient invertebrate life. Invertebrates discovered here include mostly marine...

Full citation: Mead, J.I., J.S. Tweet, V.L. Santucci, B. Tobin, C.L. Chambers, S.C. Thomas, and M.C. Carpenter, 2020. Pleistocene/Holocene Cave Fossils from Grand Canyon National Park: Ice Age (Pleistocene) Flora, Fauna, Environments, And Climate Of The Grand Canyon, Arizona. in Santucci, V.L. and J.S. Tweet, (editors), Grand Canyon National Park:...

This National Park Service report is the public version of the Chaco Culture National Historical Park paleontological resource inventory. All sensitive paleontological locality data has been redacted from this version of the report.

The Delaware Water Gap National Recreation Area’s (DEWA) geology and paleontology has been rigorously studied since 1883. In 1903, the first paleontological inventory was completed by Start B. Weller. David Parris reexamined the Silurian and Devonian strata in 1979 and 1980 with Shirley Albright, and Ordovician strata in 1984 with Kenneth Cruikshan...

Dinosaurs have captured the interest and imagination of the general public, particularly children, around the world. Paleontological resource inventories within units of the National Park Service have revealed that body and trace fossils of non-avian dinosaurs have been documented in at least 21 National Park Service areas. In addition there are tw...

The National Park Service Paleontology Program maintains an extensive collection of digital and hard copy documents, publications, photographs and other archives associated with the paleontological resources documented in 268 parks. The organization and preservation of the NPS paleontology archives has been the focus of intensive data management ac...

Chickasaw National Recreation Area (CHIC), located in south-central Oklahoma east of the Arbuckle Mountains, is best known for its wildlife and water recreation. Few visitors are aware of the important paleontological resources that occur in the park. During the summer of 2016, a comprehensive field inventory of paleontological resources within CHI...

Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally preserved specimen of a hadrosaurid dinosaur, Brachylophosaurus canadensis , from the Judith River Formation of Montana. Approximately 280 examples of the trace fossils were observed in 19 samples of gut region material. The tubular structures typically are...

Wupatki National Monument, located in north-central Arizona, encompasses over 35,000 acres of land on the southern edge of the Colorado Plateau. Geologic units outcropped on the Monument include the Toroweap (Lower Permian), Kaibab (Lower Permian), and Moenkopi (Early-Middle Triassic) formations. Each of these units preserves evidence of ancient li...

Fossil Point is an important paleontological locality situated within Lake Clark National Park & Preserve, Cook Inlet, Alaska. The locality contains one of the most productive marine invertebrate fossil sites known in Alaska. The Middle Jurassic Tuxedni Group contains exceptionally rich and diverse megainvertebrate faunas: ammonites, bivalves, and...

The Fossil Point area on the south side of Tuxedni Bay is situated within Lake Clark National Park & Preserve in south-central Alaska. This aptly named topographic feature contains one of the most productive marine invertebrate fossil sites known in Alaska. Three formations, the Red Glacier Formation, Fitz Creek Siltstone, and Cynthia Falls Sandsto...

Paleontological resource inventories for the parks of the National Park Service's Mediterranean Coast Inventory and Monitoring Network (MEDN) indicate a significant Late Cretaceous and Cenozoic fossil record for the southern California coast and islands. These inventories document over 100 million years of biologic and geologic changes along the Pa...

Paleontological resources (fossils) are any remains of past life preserved in a geologic context. Paleontological resources are non-renewable resources found in at least 232 National Park System units. Despite the abundance and diversity of these resources throughout the National Park Service (NPS), until recently few parks have had adequate baseli...

Over 20 specimens of the new genus and species Nunavutospongia irregulara, an irregular stump-like to columnar, or fan- to blade-shaped, hexactinosid hexactinellid sponge, have been recovered from exposures of the Upper Cretaceous upper Kanguk Formation on Devon Island, Nunavut Territory, in the Canadian High Arctic. The species and genus are chara...

An exceptionally preserved subadult specimen (JRF 115H) of a hadrosaurid, Brachylophosaurus canadensis, from the Judith River Formation near Malta, Montana, contains abundant plant fragments concentrated within the body cavity. We examined the taphonomy of the carcass and analyzed the gut-region material to test whether the organic remains represen...

As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, Arctic Canada,...