Protastacus
| Protastacus Temporal range:
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| Illustration of aP. politusfossil | |
Scientific classification
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Infraorder: | Astacidea |
| Superfamily: | †Protastacoidea Albrecht, 1983 |
| Family: | †Protastacidae Albrecht, 1983 |
| Genus: | †Protastacus Albrecht, 1983 |
| Type species | |
| †Astacuspolitus Schlüter, 1868
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| Species | |
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| Synonyms | |
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P. antiquussynonymy:
P. politussynonymy:
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Protastacusis anextinctgenusofdecapodcrustaceansthat lived in what is now Germany during theearly Cretaceousperiod. Thetype speciesisP. politus,and a second species,P. antiquus,is also assigned to the genus.Protastacusgrew to around 10 cm (3.9 in) long and had a mostlycrayfish-like appearance, with enlargedpincer-bearing appendages and a segmentedabdomen.Though formerly assigned to theAstacidaeorNephropoidea,it is currently placed as the only genus in thefamilyProtastacidae,which in turn is the only family in thesuperfamilyProtastacoidea.
Both known species are believed to bebrackish wateranimals, inhabiting a large upland-surrounded lake where theBückeberg Formationwas deposited during the earliest Cretaceous. This lake was originally freshwater and connected to theBoreal Sea,but became brackish due tomarine transgression.Protastacuswould have lived alongside various fish,invertebratesand aquatic reptiles in this lake, whileterrestrial animalssuch asdinosaursinhabited the surrounding shores.
Discovery and naming
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Fossils ofProtastacushave been described 115 years before the genus was established. In 1868, Schlüter erected the speciesAstacuspolitusbased on remains found nearOchtrup,Germany,believing it represented an extinct species of the extantcrayfishgenusAstacus.[1]Later in 1905, Erich Harbort studies fossilized remains in clayironstonegeodesfound north ofBückeberg,Germanyand erects the speciesAstacus antiquusbased on them. Harbort notes the similarity betweenA. politusandA. antiquus,and that the two species differ in the shape of thecarapaceanduropods.The specific nameantiquusisLatinmeaning "ancient".[2]
Albrecht (1983) is the first to recognize that the two aforementioned species do not actually belong toAstacus.He erects the genusProtastacuswithA. politusas itstype speciesandA. antiquusas an additional species. The two are thus renamed asProtastacus politusandProtastacus antiquusrespectively.[3]
Description
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A crustacean of moderate size, Harbort (1905) noted that larger specimens ofProtastacusare around 10 cm (3.9 in) long.[2]Thecarapaceis smooth and subcylindrical in shape, with a deep cervical groove stretching across its surface. This groove first bends down the carapace sides, then bends forwards, down and forwards again to reach the front of the carapace. There are no postcervical or branchiocardiac grooves. Two keel-like projections are present lower on the sides, as well as a thorn-like structure at the front of either side at the "cheek" area. Though the ends of theantennaeare not preserved, their bases were enlarged.[1]
The first three pair ofpereiopodsend withpincers,with the frontmost pair being most greatly enlarged.[3]The first segment of theabdomenis small, whereas the second to sixth segments are larger and around the same size. Theexoskeletalparts of these segments arelaterallyrounded and enlarged, giving the appearance that these segments are bulging at the bottom. Like the carapace, the covering of the abdomen is smooth. Thetelsonhas a subrectangular shape and theuropodsare large, with theexopodsbeing divided by a distinct suture known as the diaeresis.[1][4]
Classification
[edit]Although bothProtastacusspecies were initially described as species ofAstacus,Albrecht (1983) recognized that they form a distinct genus belonging in a separate family fromAstacus.He named this family Protastacidae, assigning the two generaProtastacusandPseudastacusinto it, the former being thetype genusof the family.[3]In 1997, Tshudy and Babcock reassignedPseudastacusto the familyChilenophoberidae,leaving Protastacidae as amonotypic familywithProtastacusas its only genus.[5]
The phylogenetic placement of Protastacidae has been a subject of controversy. Shenet al.(2001) and Schram (2001) questioned the family's placement in Astacida.[6][7]In 2003, Rode and Babcock found thatProtastacusbelonged to the familyAstacidae,making Protastacidae an invalid grouping.[8]From 2009 to 2012, Protastacidae was commonly placed in the superfamilyNephropoideaas relatives to the lobster familyNephropidae.[9][10][11]Analysis by Karasawaet al.(2013) found that Protastacidae contained only the genusProtastacusand belonged in a monotypicsuperfamily(Protastacoidea), which is asister taxonto the clade containingAstacoideaandParastacoidea.The following cladogram shows the placement ofProtastacuswithinAstacideaaccording to the study:[4]
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Paleoenvironment
[edit]Both of the knownProtastacusspecies were collected fromearly Cretaceousdeposits in Germany. Although Schlüter (1868) does not specify the horizon from which the fossils ofP. polituswere collected, Harbort (1905) states they most likely originate from the "upper Wealden", which is also whereP. antiquusfossils were discovered.[1][2]The "upper Wealden" here likely refers to theBückeberg Formation,sometimes called the "German Wealden" due to its similarity to the BritishWealden Group.[12]Protastacusis believed to be abrackish wateranimal, as analysis ofhydrogen,carbonandsulphurratios as well as the presence ofBotryococcusalgae in the Bückeberg Formation prove the depositional environment was brackish-freshwater.[13]
The Bückeberg Formation likely represented a largelakereceiving fluvial drainage from the surrounding uplands and connected to theBoreal Seato the west by narrow passage. Though originally freshwater, this lake gradually became brackish due tomarine transgressioncaused by episodic transgressive phases and tectonic activity.[14][15]Fossil remains of various aquatic animals have been found here which would have lived alongsideProtastacus,such asmolluscs,crustaceans,fish (hybodonts,IndaginilepisandScheenstia), turtles (includingHylaeochelys,PleurosternonandDorsetochelys(=Ballerstedtia)[16]), the plesiosaurBrancasaurus,and crocodyliforms (GoniopholisandPholidosaurus).Terrestrial animalsthat would have lived on the lake shores are also represented, including body fossils of the dinosaursStenopelixandHylaeosaurus,as well as footprints of various dinosaurs andpterosaurs.[17][18]
References
[edit]- ^abcdvon der Marck, W.; Schlüter, C. (1868).Neue fische und krebse aus der kreide von Westphalen(PDF).Stuttgart: Palaeontographica. pp. 269–305.OCLC39999779.
- ^abcHarbort, Erich (1905)."Die Fauna der Schaumburg-Lippe'schen Kreidemulde"(PDF).Abh. Königl. Preuss. Geol. Landesanstalt.45:17–24.
- ^abcAlbrecht, von Henning (1983)."Die Protastacidae n. fam., fossile Vorfahren der Flußkrebse?"(PDF).Neues Jahrbuch für Geologie und Paläontologie, Monatsberichte(1): 5–15.doi:10.1127/njgpm/1983/1983/5.
- ^abKarasawa, Hiroaki; Schweitzer, Carrie E.; Feldmann, Rodney M. (2013-01-01)."Phylogeny and systematics of extant and extinct lobsters".Journal of Crustacean Biology.33(1): 78–123.doi:10.1163/1937240X-00002111.ISSN0278-0372.
- ^Tshudy, D.; Babcock, L.E. (1997-01-01)."Morphology-based phylogenetic analysis of the clawed lobsters (family Nephropidae and the new family Chilenophoberidae)".Journal of Crustacean Biology.17(2): 253–263.doi:10.1163/193724097X00288.ISSN0278-0372.
- ^Shen, Yanbin; Schram, Frederick R.; Taylor, Rod S. (2001-01-01)."Morphological variation in fossil crayfish of the Jehol biota, Liaoning Province, China and its texonomic discrimination".Chinese Science Bulletin.46(1): 26–33.Bibcode:2001ChSBu..46...26S.doi:10.1007/BF03183202.ISSN1861-9541.S2CID89367581.
- ^Schram, Frederick R. (2001)."Phylogeny of decapods: Moving towards a consensus".In Paula, José P. M.; Flores, Augusto A. V.; Fransen, Charles H. J. M. (eds.).Advances in Decapod Crustacean Research.Developments in Hydrobiology. Dordrecht: Springer Netherlands. pp. 1–20.doi:10.1007/978-94-017-0645-2_1.ISBN978-94-017-0645-2.
- ^Rode, Alycia L.; Babcock, Loren E. (2003-01-01)."Phylogeny of Fossil and Extant Freshwater Crayfish and Some Closely Related Nephropid Lobsters".Journal of Crustacean Biology.23(2): 418–435.doi:10.1163/20021975-99990351.ISSN0278-0372.
- ^De Grave, Sammy; Pentcheff, N. Dean; Ahyong, Shane T.; Chan, Tin-Yam; Crandall, Keith A.; Dworschak, Peter C.; Felder, Darryl L.; Feldmann, Rodney M.; Fransen, Charles H. J. M.; Goulding, Laura Y. D.; Lemaitre, Rafael; Low, Martyn E. Y.; Martin, Joel W.; Ng, Peter K. L.; Schweitzer, Carrie E. (2009)."A Classification of Living and Fossil Genera of Decapod Crustaceans".The Raffles Bulletin of Zoology Supplement.21:1–109.hdl:10088/8358.ISSN0217-2445.
- ^Schweitzer, Carrie; Feldmann, Rodney; Garassino, Alessandro; Karasawa, Hiroaki; Schweigert, Günter (2010-01-07).Systematic List of Fossil Decapod Crustacean Species.BRILL.ISBN978-90-474-4126-7.
- ^Schram, Frederick; Klein, Carel von Vaupel (2012-03-20).Treatise on Zoology - Anatomy, Taxonomy, Biology. The Crustacea, Volume 9 Part B: Decapoda: Astacidea P.P. (Enoplometopoidea, Nephropoidea), Glypheidea, Axiidea, Gebiidea, and Anomura.BRILL.ISBN978-90-04-17673-7.
- ^Hornung, Jahn J.; Böhme, Annina; Reich, Mike (2012). "The 'German Wealden' and the Obernkirchen Sandstone – an Introduction".Dinosaur Tracks 2011. An International Symposium, Obernkirchen, April 14-17, 2011. Abstract Volume and Field Guide to Excursions.Universitätsverlag Göttingen. pp. 62–72.
- ^Froidl, Felix; Littke, Ralf; Baniasad, Alireza; Zheng, Tianyu; Röth, Joschka; Böcker, Johannes; Hartkopf-Fröder, Christoph; Strauss, Harald (2021-02-01)."Peculiar Berriasian" Wealden "Shales of northwest Germany: Organic facies, depositional environment, thermal maturity and kinetics of petroleum generation".Marine and Petroleum Geology.124:104819.Bibcode:2021MarPG.12404819F.doi:10.1016/j.marpetgeo.2020.104819.ISSN0264-8172.S2CID228986602.
- ^Pelzer, Guido (1998).Sedimentologie und Palynologie der Wealden-Fazies im Hannoverschen Bergland(in German). Senckenbergische Naturforschende Gesellschaft.ISBN978-3-929907-49-0.
- ^Mutterlose, Jörg; Bornemann, André (December 2000)."Distribution and facies patterns of Lower Cretaceous sediments in northern Germany: a review".Cretaceous Research.21(6): 733–759.Bibcode:2000CrRes..21..733M.doi:10.1006/cres.2000.0232.
- ^Pérez-García, A. (2014-05-01)."Revision of the poorly known Dorsetochelys typocardium, a relatively abundant pleurosternid turtle (Paracryptodira) in the Early Cretaceous of Europe".Cretaceous Research.49:152–162.Bibcode:2014CrRes..49..152P.doi:10.1016/j.cretres.2014.02.015.ISSN0195-6671.
- ^Böhme, Annina; Reich, Mike; Hornung, Jahn J.; Karl, Hans-Volker (2012). "Northern 'German Wealden' – the collection of the Göttingen University".Dinosaur Tracks 2011. An International Symposium, Obernkirchen, April 14-17, 2011. Abstract Volume and Field Guide to Excursions.Universitätsverlag Göttingen. pp. 62–72.
- ^Sachs, Sven; Hornung, Jahn J. (2013-04-03). Evans, David C. (ed.)."Ankylosaur Remains from the Early Cretaceous (Valanginian) of Northwestern Germany".PLOS ONE.8(4): e60571.Bibcode:2013PLoSO...860571S.doi:10.1371/journal.pone.0060571.ISSN1932-6203.PMC3616133.PMID23560099.
External links
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Media related toProtastacusat Wikimedia Commons
