STRATIGRAPHY AND DEPOSITIONAL ENVIRONMENT

The formation that includes "Sharktooth Hill" is locally referred to by geologists as the "Round Mountain Silt". Located in Kern County, California, it was deposited by a river delta coming out of the mountains to the east of Bakersfield. At this time (Middle Miocene) most of central California was covered by a small sea. The transformation of Bakersfield area from beachfront to near-desert could be summed up as the result of the overall trend of falling sea level, significant uplift of the Sierra Nevadas, and gradual landlocking of the Temblor Sea. The Southern Bakersfield region continued to exist as a swampy area well into the Pleistocene. At the same time the Miocene deposits eroded into a hilly area with many gullies exposing the so-called "Upper Layer of the Round Mountain Silt". This is the layer containing the bonebed which has yielded the most diverse and best-studied Tertiary fossil marine vertebrate assemblage yet known from anywhere within the Pacific Realm.

This fossil assemblage, called the Sharktooth Hill Local Fauna (Wood et al., 1941), is comprised of more than one hundred species of sharks, rays, bony fish, turtles, birds and mammals, including terrestrial species from the adjacent Miocene land mass (south of where Bakersfield currently is located). The "Round Mountain Silt" covers approximately 110 square miles. The Sharktooth Hill Bonebed is a single, relatively thin, but widespread horizon -- this fossil producing layer is only 6-8" thick (with some exceptions). The STH Bonebed was recently assigned a Middle Miocene age between 15.2 and 16.0 million years old by Sanchez & Prothero (2003).

Correlation chart integrated by Jim Bourdon 2008. Paleomap reproduced with the permission of Dr. Blakey 2007.

In 1998, the original species list obtained from the Buena Vista Museum (BVMNH) included unfamiliar taxa with unlocatable descriptions. Elements of this list remain below as placeholders for those potential tooth-designs. In addition, taxa attributed at times to the STH fauna but which more likely originated from other horizons are still included in the list. In this case, the taxon will be flagged as not present in the fauna. Otherwise, included species appear to be valid components of the fauna.

Many of the species have now been linked to the website's Genus pages; however, some continue to have standalone pages that support them. The below shark fauna incorporate not only the authors' observations but also input and help from Steve Alter, Bill Heim, Gordon Hubbell, Larry Martin, Walter Hunt, Hideo Yabe and others.

Scarcity

Rare	- One or two specimens found each year (by all collectors).
Scarce	- A regular collector may find one or two a year.
Uncommon	- A collector may find one every few trips.
Common	- A specimen can be found each trip.
Abundant	- Pretty hard not to find a number of specimens each trip

CLICK ON SPECIMEN IMAGES FOR ADDITIONAL DETAILS
	A supporting genus page is not available.
	Taxa sometimes attributed to the fauna, but which can't be substantiated, will include this icon.
HEXANCHIFORMES
	Hexanchus andersoni JORDAN, 1907 Extinct Sixgill shark. Parasymphyseals are relatively common in the fauna, but complete anterolaterals are uncommon to scarce.
	Notorynchus sp - Sevengill shark. Notorynchus was originally reported on this page, however it is now thought that this genus may not be present in the STH fauna. The presented example may have originated from another horizon or is a mesio-distally compressed Hexanchus lower.
SQUALIFORMES
	Echinorhinus blakei AGASSIZ, 1856 Bramble shark A scarce species from Bakersfield, CA, The accompanying tooth is only 1.5 cm wide x 1cm high. Welton (1979) limited the occurrence of blakei to the STH bonebed and considered those from Pyramid Hill & Olcese Sands closer to E. cookei.
	Squalus occidentalis (AGASSIZ, 1856) Dogshark Originally listed as Squalus serriculus JORDAN & HANNIBAL 1923 this is now deemed a junior synonym of S. occidentalis1. Some prefer the more conservative Squalus sp. These teeth are quite abundant in the fauna.
SQUATINFORMES
	Squatina lericheii JORDAN & BEAL, 1913 Angel shark These teeth are quite common and may actually represent the extant species S. californica AYRES, 1859.2
HETERODONTIFORMES
	Heterodontus -- Bullhead shark The illustrated tooth is 3.0 mm in height. Based on studied material, these teeth are relatively common and are easily confused with male dasyatid teeth or are thought to be from skates, unless observed under magnification.
LAMNIFORMES
	Carcharias taurus (RAFINESQUE, 1810) Extant Sand Tiger. There appears to be no evidence of Carcharias teeth in the STH fauna. Reports to the contrary likely result from specimens found in the Olcese Sand where this tooth-design is somewhat common.
	?Megachasma sp - Megamouth shark. Known from the Pyramid Hill Sand and Freeman Silt (both Early Miocene) there are no verifiable reports from STH or later sediments. These West coast teeth are significantly different than Lee Creek specimens and the extant species; possibly a different genus or species.
	Alopias ?latidens (LERICHE 1909) extinct Thresher shark Thresher teeth are a relatively rare component of the fauna.
	Cetorhinus sp — Basking shark Originally identified as C. cf maximus (GUNNER 1765) it now seems more appropriate to go with a more conservative identification. These teeth are deemed a common component of the fauna.
	Carcharocles chubutensis (AMEGHINO, 1906) extinct Mega-toothed shark Chubutensis teeth are not represented in the STH fauna. They are found (accompanying tooth) in older Miocene units in the area (Olcese Sand, Pyramid Hill Sand).
	Carcharocles megalodon (AGASSIZ, 1837) extinct Mega-toothed shark. Jordan (1907) deemed these teeth different from their right coast counterparts erecting Carcharodon branneri. Leriche (1908) deemed them Carcharodon megalodon and Jordan & Beal (1913) followed suit.
	Cosmopolitodus (Isurus) planus (AGASSIZ, 1856) extinct White shark This tooth-design is abundant in the STH fauna.
	Cosmopolitodus (Isurus) hastalis (AGASSIZ, 1843) extinct White shark Teeth from this species are characterized by the broad flat labial root face. They are abundant in the STH fauna.
	Cosmopolitodus sp (serrate, a.k.a. xiphodon) extinct White shark There is no evidence that serrate hastalis teeth are represented in the STH fauna. The accompanying specimen although purported from the fauna is more likely from another horizon or location.3
	Carcharodon sp - Great White shark Carcharodon has been attributed to the fauna (including this website4); but a detailed review of well documented specimens and personal collecting history requires it to be removed. The accompanying image, originally ascribed to STH likely originated from a different location and horizon.
	Isurus oxyrinchus RAFINESQUE, 1809 aka I. desori (SISMONDA, 1849) Shortfin Mako shark Relatively uncommon in the STH fauna.
	Isurus retroflexus (AGASSIZ, 1843) aka I. paucus GUITART MANDAY, 1966 Longfin Mako shark Mako teeth with labio-lingually compressed crowns are rare in the STH fauna.
	Parotodus benedeni (LeHON, 1871) extinct False Mako shark. Teeth from this species are scarce in the fauna.
CARCHARHINIFORMES
SPECIMEN REQUIRED	Cephaloscyllium -- Swellshark. This Applegate determination was included in the fauna by Mitchell (1965) but not figured. An illustration or representative example of this tooth-design has not been seen.
	cf Scyliorhinus -- Catshark. This Larry Martin specimen is from the Round Mountain Silt. This may be the design that served as the basis of the Cephaloscyllium identification above.
	Galeorhinus sp - Tope shark. Although scarcely found with complete roots, Galeorhinus teeth are common in the fauna. These teeth are not Jordan & Beal's (1913) G. hannibali which compares better with the Galeocerdo tooth-design.
	Triakis sp - Houndshark. The BVMNH faunal list included Triakis beali JORDAN, 1919; there is question about the validity of that taxon. The accompanying STH specimen is similar to the extant Triakis scyllium MÜLLER & HENLE, 1839
	Mustelus sp - Smooth-hound shark. Teeth thought to represent Mustelus are present in the STH fauna; due to their size (about 1mm high or wide) they slip past most screens or go unrecognized as fossils to the untrained eye.
	Hemipristis serra AGASSIZ, 1843 Snaggletooth shark. Snaggletooth teeth from this site were originally assigned to H. heteropleurus Agassiz and H. chiconis Jordan (1907). There are no characteristics of these teeth that distinguish them from their east coast counterparts.
GOOD LUCK	Carcharhinus antiquus (AGASSIZ, 1856) This species was included in the BVMNH faunal list, but the illustration in Jordan (1907) was of poor quality and the tooth damaged. Jordan (1907) had originally identified this tooth as Agassiz's Prionodon antiquus but placed it in the genus Carcharias and in 1913, moved it to Carcharhinus but speculated it might be Carcharodon, possibly C. rectus.
	Carcharhinus cf "egertoni" (AGASSIZ, 1843) extinct requiem shark. BVMNH faunal list, illustration not seen. The underlying validity of this taxon remains in question due to the possibility it includes teeth from multiple species.
	Carcharhinus cf limbatus (VALENCIENNES, 1839) Blacktip shark
	Carcharhinus obscurus (LeSUEUR, 1818) Dusky shark Very scarce in the STH fauna.
	Galeocerdo aduncus (AGASSIZ, 1843) extinct Tiger shark Jordan (1907) followed Agassiz and attributed these teeth to G. productus AGASSIZ, 1853. Leriche (1908) subsequently indicated that they were identical to G. aduncus; but, Jordan (1913) rejected this notion based on geographic considerations.
	Physogaleus contortus (GIBBES, 1849) extinct Tiger-like shark. The illustrated specimen measures 15.0 mm in height; common in the STH fauna.
	Sphyrna cf zygaena (LINNAEUS, 1758) — Hammerhead shark These teeth have been reported as Sphyrna ?laevissima
SPECIMEN REQUIRED	Sphyrna cf media SPRINGER, 1940 — Hammerhead shark
RAJIFORMES
	"Rhinobatos" sp - Guitarfish. Relatively common in the fauna, these guitarfish-like teeth are rarely collected due to their sub-1mm size. Some aspects of the crown and root-design require the genus determination to be treated as speculative.
	Raja sp - Skate. Unlike Lee Creek where skate teeth can be quite large and common, the accompanying Round Mountain Silt tooth is just over 1mm in height and might be deemed scarce in the fauna.
MYLIOBATIFORMES
	Dasyatis spp - Stingray. There appears to be three common stingrays in this fauna, the accompanying image is a high-cusped male of one of these tooth-designs..
	Gymnura sp - Butterfly Rays. Finding examples of this genus requires the retention and processing of 1mm-class material; the accompanying image is from the Round Mountain Silt. These teeth should be viewed as uncommon in the fauna.
	Mobula loupianensis CAPPETTA, 1970 -- extinct devil ray. The illustrated male tooth is 2 mm high. These teeth are only 1/10th as common as those from stingrays, but are still common within the fauna.
EXAMPLE REQUIRED	Myliobatis merriami JORDAN & BEAL, 1913. In the STH myliobatid material, there appears to be Myliobatis and another design more reminiscent of Pteromylaeus; a third myliobatid may also be present. Referring to the 1913 illustration, this tooth-design may be Pteromylaeus.
EXAMPLE REQUIRED	Myliobatis smithii (JORDAN & BEAL, 1913) These teeth were originally placed in Rhinoptera by Jordan and Beal; who reassigned them is currently unknown. I've seen hundreds of myliobatid teeth from this location, and none comparred well with the rhinopterid design. Illustrations from the original publication were unable to provide sufficient detail for a better identification.