Tags

Type your tag names separated by a space and hit enter

A new calmanostracan crustacean species from the Cretaceous Yixian Formation and a simple approach for differentiating fossil tadpole shrimps and their relatives.
Zoological Lett 2019; 5:20ZL

Abstract

Background

Calmanostraca is a group of branchiopod eucrustaceans, with Triops cancriformis and Lepidurus apus as most prominent representatives. Both are regularly addressed with the inaccurate tag "living fossil", suggesting that the morphology has remained stable for several millions of years. Yet, T. cancriformis and L. apus represent only a fraction of the morphological diversity occurring in Calmanostraca, comprising the two groups Notostraca and Kazacharthra. Notostracans, commonly called tadpole shrimps, comprise the two groups Lepidurus and Triops with their elongated and rather narrow (in dorsal view) head shields. Kazacharthrans are exclusively fossil calmanostracans with broad and rather short shields, known from the Jurassic and Triassic period. One formation where fossil calmanostracans have been found is the Yixian Formation of northeastern China (Lower Cretaceous, 125-121 million years). It is part of the Jehol Group, an ecosystem known for its exceptionally well-preserved fossils, including vertebrates and plants, but also diverse arthropods. Two calmanostracan species have to date been described from the Yixian Formation, Jeholops hongi and Chenops yixianensis.

Results

We describe here a new calmanostracan crustacean from the Yixian Formation, Notostraca oleseni, and additionally a simple tool using a morphospace analysis to delineate different species. Measurements characterising the shield and trunk proportions of different calmanostracan species were performed, data were size-corrected, and used for this morphospace analysis to compare the different morphologies. As sclerotised body parts are more likely to be preserved in fossils than soft tissue, shields and parts of the trunk are in many cases the only morphological structures available for study. Therefore, the present analysis represents a simple tool for distinguishing between different species, as well as allowing the inclusion of specimens that are only preserved fragmentarily. Additionally, it provides a tool to demarcate the kazacharthran-like specimen described, but not formally named, by Wagner et al. (Paleontol Res. 22:57-63, 2018). Hence, we amended the description and name the species Calmanostraca hassbergella.

Conclusion

Our results indicate a large diversity in shield and trunk morphology in calmanostracans, in contrast to their often claimed highly conserved and uniform morphology. Especially extinct forms such as Notostraca oleseni add up to this result and point to the species richness and morphological diversity within Calmanostraca.

Authors+Show Affiliations

1Department of Biology II, LMU Munich, Biocenter, Groβhaderner Str. 2, 82152, Planegg-Martinsried, Germany.1Department of Biology II, LMU Munich, Biocenter, Groβhaderner Str. 2, 82152, Planegg-Martinsried, Germany. 2GeoBio-Center der LMU München, Richard-Wagner-Str. 10, 80333 Munich, Germany.1Department of Biology II, LMU Munich, Biocenter, Groβhaderner Str. 2, 82152, Planegg-Martinsried, Germany. 2GeoBio-Center der LMU München, Richard-Wagner-Str. 10, 80333 Munich, Germany.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31245037

Citation

Wagner, Philipp, et al. "A New Calmanostracan Crustacean Species From the Cretaceous Yixian Formation and a Simple Approach for Differentiating Fossil Tadpole Shrimps and Their Relatives." Zoological Letters, vol. 5, 2019, p. 20.
Wagner P, Haug JT, Haug C. A new calmanostracan crustacean species from the Cretaceous Yixian Formation and a simple approach for differentiating fossil tadpole shrimps and their relatives. Zoological Lett. 2019;5:20.
Wagner, P., Haug, J. T., & Haug, C. (2019). A new calmanostracan crustacean species from the Cretaceous Yixian Formation and a simple approach for differentiating fossil tadpole shrimps and their relatives. Zoological Letters, 5, p. 20. doi:10.1186/s40851-019-0136-0.
Wagner P, Haug JT, Haug C. A New Calmanostracan Crustacean Species From the Cretaceous Yixian Formation and a Simple Approach for Differentiating Fossil Tadpole Shrimps and Their Relatives. Zoological Lett. 2019;5:20. PubMed PMID: 31245037.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - A new calmanostracan crustacean species from the Cretaceous Yixian Formation and a simple approach for differentiating fossil tadpole shrimps and their relatives. AU - Wagner,Philipp, AU - Haug,Joachim T, AU - Haug,Carolin, Y1 - 2019/06/18/ PY - 2018/08/17/received PY - 2019/05/21/accepted PY - 2019/6/28/entrez PY - 2019/6/28/pubmed PY - 2019/6/28/medline KW - Calmanostraca KW - Cretaceous KW - Eucrustacea KW - Jehol Group KW - Kazacharthra KW - Morphospace KW - Notostraca KW - Phylogeny KW - Species delineation KW - Yixian Formation SP - 20 EP - 20 JF - Zoological letters JO - Zoological Lett VL - 5 N2 - Background: Calmanostraca is a group of branchiopod eucrustaceans, with Triops cancriformis and Lepidurus apus as most prominent representatives. Both are regularly addressed with the inaccurate tag "living fossil", suggesting that the morphology has remained stable for several millions of years. Yet, T. cancriformis and L. apus represent only a fraction of the morphological diversity occurring in Calmanostraca, comprising the two groups Notostraca and Kazacharthra. Notostracans, commonly called tadpole shrimps, comprise the two groups Lepidurus and Triops with their elongated and rather narrow (in dorsal view) head shields. Kazacharthrans are exclusively fossil calmanostracans with broad and rather short shields, known from the Jurassic and Triassic period. One formation where fossil calmanostracans have been found is the Yixian Formation of northeastern China (Lower Cretaceous, 125-121 million years). It is part of the Jehol Group, an ecosystem known for its exceptionally well-preserved fossils, including vertebrates and plants, but also diverse arthropods. Two calmanostracan species have to date been described from the Yixian Formation, Jeholops hongi and Chenops yixianensis. Results: We describe here a new calmanostracan crustacean from the Yixian Formation, Notostraca oleseni, and additionally a simple tool using a morphospace analysis to delineate different species. Measurements characterising the shield and trunk proportions of different calmanostracan species were performed, data were size-corrected, and used for this morphospace analysis to compare the different morphologies. As sclerotised body parts are more likely to be preserved in fossils than soft tissue, shields and parts of the trunk are in many cases the only morphological structures available for study. Therefore, the present analysis represents a simple tool for distinguishing between different species, as well as allowing the inclusion of specimens that are only preserved fragmentarily. Additionally, it provides a tool to demarcate the kazacharthran-like specimen described, but not formally named, by Wagner et al. (Paleontol Res. 22:57-63, 2018). Hence, we amended the description and name the species Calmanostraca hassbergella. Conclusion: Our results indicate a large diversity in shield and trunk morphology in calmanostracans, in contrast to their often claimed highly conserved and uniform morphology. Especially extinct forms such as Notostraca oleseni add up to this result and point to the species richness and morphological diversity within Calmanostraca. SN - 2056-306X UR - https://www.unboundmedicine.com/medline/citation/31245037/A_new_calmanostracan_crustacean_species_from_the_Cretaceous_Yixian_Formation_and_a_simple_approach_for_differentiating_fossil_tadpole_shrimps_and_their_relatives_ L2 - https://zoologicalletters.biomedcentral.com/articles/10.1186/s40851-019-0136-0 DB - PRIME DP - Unbound Medicine ER -