Pohlsepia
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''Pohlsepia mazonensis'' is a species of fossil organism with unknown affinity. Although it was originally identified as an extinct
cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...
, later studies denied that interpretation. The species is known from a single exceptionally preserved
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
discovered in the late Carboniferous ( Pennsylvanian) Francis Creek Shale (
Mazon Creek fossil beds The Mazon Creek fossil beds are a conservation ' found near Morris, in Grundy County, Illinois. The fossils are preserved in ironstone concretions, formed approximately in the mid- Pennsylvanian epoch of the Carboniferous period. These concr ...
) of the Carbondale Formation, north-east
Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...
, United States. ''Pohlsepia mazonensis'' is named after its discoverer, James Pohl, and the type locality, Mazon Creek. Its
habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
was the shallows seawards of a major
river delta A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creat ...
in what at that time was an inland ocean between the
Midwest The Midwestern United States (also referred to as the Midwest, the Heartland or the American Midwest) is one of the four census regions defined by the United States Census Bureau. It occupies the northern central part of the United States. It ...
and the
Appalachians The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...
. In its initial description, it was considered to be the oldest known
octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...
, but later studies have considered this classification dubious. In 2022, it was even suggested that it may not be a mollusk. The
type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
is reposited at the
Field Museum of Natural History The Field Museum of Natural History (FMNH), also known as The Field Museum, is a natural history museum in Chicago, Illinois, and is one of the largest such museums in the world. The museum is popular for the size and quality of its educationa ...
in
Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...
,
Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...
.


Fossil

The ''Pohlsepia mazonensis'' fossil found by James Pohl is the only known example of the species. Most notably, the fossil has ten arms. The extra two arms are shorter, while the other eight are similar in length.Kluessendorf J, Doyle P. 2000 Pohlsepia mazonensis, an early "Octopus" from the Carboniferous of Illinois, USA. Palaeontology 43(5): 919-926 The wide fossil is “sack-shaped” with indistinct features including a poorly defined head. While it is unclear, one of these features could be an
ink sac An ink sac is an anatomical feature that is found in many cephalopod mollusks used to produce the defensive cephalopod ink. With the exception of nocturnal and very deep water cephalopods, all Coleoidea (squid, octopus and cuttlefish) which dwell ...
. The fossil lacks arm hooks and suckers and all of these factors combine to make the assigning of the order Cirroctopoda controversial.Eyden, Phil. “Fossil Octopuses.” The Octopus News Magazine Online, Nov. 2004, www.tonmo.com/pages/fossil-octopuses/.


Etymology

Genus name ''Pohlsepia'' is came from its discoverer James Pohl. He is the son of Joe Pohl and together they have collected fossils in the Mazon Creek area. Originally from Wisconsin and Minnesota, Pohl is a native Midwesterner. He and his father have donated their fossils to museums in the area, including ''Pohlsepia mazonensis'' to the Field Museum.


Classification

In 2000, Joanne Kluessendorf assigned ''Pohlsepia mazonensis'' to the order Cirroctopoda. Many other researchers disagreed, citing the lack of internal structure. The possible evidence of fins and the huge time difference between the ''Pohlsepia mazonensis'' fossil and first confirmed cirrate octopus fossils is problematic. However, the species can be classified as an octopod. Despite the number of arms being unclear, the fact that the fossil has an indistinct head, sac like body and similar fins to cirrate octopods gives enough evidence to classify ''Pohlsepia mazonensis'' in the order Cirroctopoda. When looking at the groups Teudopsidae, Trachyteuthididae, the Vampyromorpha, cirrate octopods, incirrate octopods and the fossil Loligosepiina, the describing authors proposed that ''Pohlsepia mazonensis'' would be most closely related to the octopods based on its lack of a shell. However, later studies found the placement within Octopoda to be dubious, due to the fossils poor preservation, and the fact that other fossils have now shown true
octopuses An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed Mollusca, mollusc of the order (biology), order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, ...
to have first arisen in the
Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
. In 2021, it is considered that is even unlikely to be cephalopod or mollusk. Lack of a shell is a highly unlikely combination in a Carboniferous cephalopod. In addition, its appendages lack hooks, suckers, cirri, an arm web, and the characteristic 8/10 arm count. There is neither a beak, unambiguous ink sac, nor radula. The bulbous body outline and presence of appendages more likely to show the affinity as a
cnidarian Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...
, a phylum of invertebrate animals including
jellyfish Jellyfish, also known as sea jellies or simply jellies, are the #Life cycle, medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animal ...
and
sea anemones Sea anemones ( ) are a group of predatory marine invertebrates constituting the order Actiniaria. Because of their colourful appearance, they are named after the '' Anemone'', a terrestrial flowering plant. Sea anemones are classified in the p ...
. In 2019, fossils included some fossils including ones from Mazon Creek like
vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...
, '' Tullimonstrum'', and ''Pohlsepia'' are examined, to consider affinity of ''Tullimonstrum''. Although this study treated ''Pohlsepia'' as cephalopod,
melanosomes A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light-absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotection ...
cannot be identified from its eyespot.


Mazon Creek

Located in what is currently northern Illinois, the Mazon Creek preserved the ''Pohlsepia mazonensis'' fossil extraordinarily. The ''Pohlsepia mazonensis'' fossil was found specifically in the Pit 11 region, within the Francis Creek Shale Member.Kluessendorf, J. and Doyle, P., 2000. Pohlsepia mazonensis, an early ‘octopus’ from the Carboniferous of Illinois, USA. Palaeontology, 43(5), pp.919-926. Like most soft tissue fossils found in Mazon Creek, it is preserved as a 2D light-on-dark discolouration of the matrix.Clements, T., Purnell, M. and Gabbott, S., 2019. The Mazon Creek Lagerstätte: a diverse late Paleozoic ecosystem entombed within siderite concretions. Journal of the Geological Society, 176(1), pp.1-11. The Francis Creek Shale Member of the Carbon Formation has a diverse array of preserved plants and animals.Baird, G. C., et al. “Taphonomy of Middle Pennsylvanian Mazon Creek Area Fossil Localities, Northeast Illinois: Significance of Exceptional Fossil Preservation in Syngenetic Concretions.” PALAIOS, vol. 1, no. 3, 1986, pp. 271–285. JSTOR, JSTOR, www.jstor.org/stable/3514690. Previously, it was thought that these organisms were immediately killed and buried in storm surges, where bursts of water would submerge the organisms in sediments, creating an environment where their remains were protected from scavengers before most decomposition could start. However, there is limited geological evidence for the hypothesis of storm surges, and the kill mechanism in the Mazon Creek is not fully understood but high sedimentation could have choked, killed, and buried organisms rapidly


References


External links


The Octopus News Magazine Online: Fossil Octopuses
{{Taxonbar, from=Q7207783 Fossil taxa described in 2000 Controversial taxa