Fossil Hunting at Post Oak Creek, Sherman, Texas

Post Oak Creek is a small, slow-moving creek that cuts through downtown Sherman, Texas, about an hour north of Dallas, exposing Late Cretaceous marine sediments of the Eagle Ford Group. The creek is one of the best-known public shark-tooth localities in the United States: collectors routinely fill a small bag with sand tiger, mako, Squalicorax, Cretolamna, and the occasional larger Cretaceous shark tooth in a few hours of screen-washing the gravel.

Because Texas treats navigable streambeds as public, invertebrate-fossil collecting is allowed at Post Oak Creek without permit or fee. The City of Sherman is in the process of acquiring roughly 100 acres around the creek to formally establish Shark Tooth Park at Post Oak Creek. Until then access is via an informal pull-off near the S. Travis Street bridge.

Location and Directions

Post Oak Creek runs through the southern half of Sherman, Texas, in Grayson County.

Directions to Post Oak Creek

The most-used informal access is the S. Travis Street bridge at approximately 2298 S Travis St, Sherman, TX 75090. Parking is currently very limited (a small shoulder pull-off). The creek bank is steep and slippery, and the descent is unmarked. Newer access points are being added as Shark Tooth Park develops.

Bring a small kitchen sieve or 1/4-inch hardware-cloth screen, a wash bucket, rubber boots or sandals (you'll be wading), insect repellent (mosquitoes in summer), and water. Best collecting is the day or two after a heavy storm, once rain has scoured fresh material from the banks and the water has dropped. Avoid the creek during or right after major rainfall when water levels are dangerous.

What Fossils You'll Find

The Eagle Ford Group at Sherman records a transgressive marine cycle deposited between roughly 95 and 90 million years ago in the early Late Cretaceous (Cenomanian–Turonian), when the Western Interior Seaway flooded across central North America and joined the Gulf of Mexico to the Arctic Ocean.

Shark teeth are by far the most common find. Most published trip reports describe a few dozen small teeth recovered in a half-day visit, with experienced collectors who screen-wash gravel returning home with several hundred. The most frequently encountered species is the slender-toothed goblin shark Scapanorhynchus texanus, recognised by its long, narrow, sharply striated crowns. The lemon-sized teeth of Cretolamna appendiculata are also abundant, as are the small triangular teeth of the scavenging Squalicorax kaupi and the larger, smooth-edged blades of Cretodus crassidens. The durophagous shark Ptychodus, which crushed shells with low pavement-like teeth, leaves distinctive square-faced fossils that look almost like worn molars. Most prized of the common species is the early member of the Otodus lineage, Cretoxyrhina mantelli (the "Ginsu shark"), whose large blades occasionally turn up in the creek.

Less common but regular finds include ammonite fragments (Sciponoceras, Acanthoceras), the prized fangs of the bony fish Enchodus (the "saber-toothed herring"), pieces of Inoceramus shell, scattered fish vertebrae and bone, ray dermal denticles, and the occasional small mosasaur tooth, at this age in Texas, most likely from a primitive plioplatecarpine. Larger and more complete specimens are rare but documented in the local collector community. Partial Ptychodus crushing pads and articulated Enchodus jaw fragments have all come from Post Oak Creek over the years.

"One of the most popular places in Texas to find shark teeth is nearly four hundred miles from the sea." Texas Monthly

Geologic History

The Eagle Ford Group was deposited during the early Late Cretaceous as global sea levels reached one of their highest points in Phanerozoic history and the Western Interior Seaway flooded southward from the Arctic to meet the Gulf of Mexico across central North America. North Texas lay on the eastern margin of this seaway, in shallow but well-stratified water close to the paleo-shoreline of the Sabine and Llano uplifts. Dark, organic-rich shales, marls, and thin limestones accumulated on the seafloor under chronically low-oxygen conditions that prevented scavenging and bioturbation, preserving fish, sharks, and ammonites in great numbers.

The Eagle Ford itself is divided into the lower Britton Member and the upper Arcadia Park Member in this region. Both produce fossils at Post Oak Creek, with the gravel bars concentrating teeth that have weathered out of both members as the creek cuts across the section. Sherman sits near the structurally elevated Preston Anticline, which brings the Eagle Ford close to the surface here despite the great regional dip of the Cretaceous section toward the Gulf of Mexico.

Active Holocene erosion of Post Oak Creek has cut through the Eagle Ford and continuously winnows fresh fossil material from the bedrock into the modern streambed. Heavy storms and prolonged spring rains wash out new teeth and re-expose old gravel bars. The day or two after a storm is consistently the most productive collecting window. The creek bed also reworks a thin lag of Pleistocene gravels and the occasional ice-age mammal bone from the overlying alluvial terraces.

How Post Oak Creek Came to Be a Collecting Site

Local Sherman collectors have worked Post Oak Creek since at least the 1950s, and the creek has been a Dallas Paleontological Society and North Texas amateur fossil-hunting destination for decades. Texas treats navigable streambeds, including most perennial creeks, as public, with collection of invertebrate fossils and shark teeth permitted for personal use. The Texas Parks and Wildlife Department, Texas Historical Commission, and Texas Game Wardens enforce restrictions on collecting vertebrate fossils on state lands and on collecting Native American artifacts anywhere.

The City of Sherman has been working since the early 2020s on a more formal fossil park around Post Oak Creek. About 50 acres of additional land have been acquired alongside city-owned ground, and the planned Shark Tooth Park at Post Oak Creek will eventually cover roughly 100 acres with improved trailheads, parking, interpretive signage, and (potentially) a small visitor centre. Until the park is fully developed, collectors continue to rely on the informal pull-off near the S. Travis Street bridge.

Collecting Rules & Regulations

Is Fossil Collecting Allowed?

Yes, for invertebrate fossils, shark teeth, and other non-vertebrate material taken in reasonable amounts for personal (non-commercial) use.

Key Points:

Free public access. No permit or fee for invertebrate collection
Stay in the streambed. Do not dig into private banks above the high-water mark
Vertebrate fossils on federally administered lands are off-limits. On private land in Texas, ownership rules apply
No collecting Native American artifacts (stone tools, projectile points)
Park legally on public road shoulders only

Post Oak Creek Fossil Hunting Guide