Allocrioceras
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''Allocrioceras'' is an
ammonoid Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...
cephalopod from the
Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...
to
Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya ( million years ago) and 83.6 ± 0.7 m ...
stages of the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
, included in the turrilitoid family
Anisoceratidae Anisoceratidae is an extinct Family (biology), family of heteromorph ammonites which belong to the Ancyloceratina superfamily Turrilitoidea. Members of the family range is from the lower Albian to the upper Turonian. The family is possibly deriv ...
. Its shell is strongly ribbed and is in the form of a widely open spiral.


Classification

After its 1907 discovery, the species ''A. hazzardi'' was erroneously classified as '' Crioceras latus'' by Udden. A later 1928 revision by Adkins removed it from the species ''C. latus'' while keeping it as a member of the genus ''Crioceras''. In 1963, Young gave the species its final classification in a new genus, ''Allocrioceras'', originally defined by Spath in 1926.


Biology

''Allocrioceras'' was small compared to some Ammonites. Its shell diameter was only a bit larger than an U.S. quarter. Unlike most Ammonites its shell was partially uncoiled. Ammonites like this, with shell configurations differing from the typical tightly coiled spiral, are called
heteromorph The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and bec ...
s. It lived approximately 88 million years before present during the
Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...
stage
Cretaceous Period The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 77.1 million years, it is the ninth and longest geologi ...
in what is now
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
. Its fossils can be found in the
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
s of Brewster and Terrel counties. Its stomach contents and some soft parts have been preserved in a fossil specimen of the species ''A.'' cf. ''annulatum'' found in the
Sannine Formation The Sannine Formation, also called the Sannine Limestone, is a Cretaceous geologic formation in Lebanon. It is a Konservat-Lagerstätte that contains a high diversity of well-preserved fish, reptiles, and invertebrates from the Tethys Ocean wit ...
of
Lebanon Lebanon, officially the Republic of Lebanon, is a country in the Levant region of West Asia. Situated at the crossroads of the Mediterranean Basin and the Arabian Peninsula, it is bordered by Syria to the north and east, Israel to the south ...
, which show it preyed on comatulid
crinoid Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are ...
s and was a pelagic,
aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...
-upwards drifter.


Distribution

Fossils of ''Allocrioceras'' have been found in Colombia (Loma Gorda Formation, Aipe, Huila),Patarroyo, 2011 France, Germany, Lebanon, South Africa, Ukraine, the United Kingdom, and the United States (Arizona, Montana, New Mexico, Texas, Utah).''Allocrioceras''
at
Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...
.org


References


Bibliography

* Ammonitida genera Heteromorphic ammonites Turonian genus first appearances Santonian genus extinctions Ammonites of Africa Cretaceous Africa Late Cretaceous ammonites of Europe Late Cretaceous ammonites of North America Cretaceous United States Ammonites of South America Cretaceous Colombia Fossil taxa described in 1926 Turrilitoidea {{ammonitida-stub