{{Short description|Extinct genus of arthropods}} {{Automatic taxobox | fossil_range = {{Geological range|Cambrian Stage 3}} | image = Kuamaia.png | image_caption = Fossil of ''Kuamaia lata'' including under normal light and tomographic view, with accompanying drawing | display_parents = 3 | taxon = Kuamaia | authority = Hou 1987 | subdivision_ranks = Species | subdivision = *'''''Kuamaia lata''''' <small>Hou 1987</small> * '''''Kuamaia muricata''''' <small>Hou and Bergström 1997</small> }}
'''''Kuamaia''''' is an extinct genus of marine Cambrian arthropod belonging to Conciliterga, which is part of the broader group Artiopoda (which contains trilobites and their close relatives).<ref>{{Cite journal |title=Arthroaspis n. gen., a common element of the Sirius Passet Lagerstätte (Cambrian, North Greenland), sheds light on trilobite ancestry |last1=Stein |first1=Martin |last2=Budd |first2=Graham E |date=2013-05-11 |page=99 |doi=10.1186/1471-2148-13-99 |pmc=3662621 |pmid=23663519 |last3=Peel |first3=John S |last4=Harper |first4=David AT|journal = BMC Evolutionary Biology|volume = 13 |doi-access=free }}</ref><ref>{{Cite web |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=167498 |title=Fossilworks: Kuamaia lata |website=fossilworks.org |publisher=Fossilworks |access-date=17 December 2021}}</ref> Fossils of the type species ''K. lata'' were discovered in the Chengjiang biota. The other species in the genus, ''K. muricata'' has also been identified there, but neither species has been found elsewhere.<ref name=":0">{{Cite book|title=The Cambrian fossils of Chengjiang, China: the flowering of early animal life|others=Hou, Xianguang.|date=8 March 2017 |isbn=978-1-118-89631-0|edition=Second|location=Chichester, West Sussex|oclc=970396735}}</ref>
== Morphology == thumb|left|Reconstruction of ''Kuamaia lata'' ''Kuamaia'' has an oval dorsal exoskeleton (tergite) shape, with a gradual decline from the somewhat elevated medial axis of the animal to the exoskeleton edge. The surface appears smooth, with little space between tergites and low-profile pleural (lateral) spines. The cephalon (head shield) is trapezoid and wider than long. The thorax has 7 or 8 segments. The pygidium (tail) has 2 or 3 pairs of lateral spines and 1 terminal spine. The body length (excluding appendages) ranges between 1.4 cm and 7.9 cm for ''K. lata''<ref name=":3" /> and 1.48 cm for ''K. muricata''.<ref name=":4">{{Cite book |last=Hou |first=Xianguang |title=Arthropods of the Lower Cambrian Chengjiang fauna, southwest China |last2=Bergström |first2=Jan |date=1997 |publisher=Scandinavian Univ. Press |isbn=978-82-00-37693-4 |series=Fossils and Strata |location=Oslo}}</ref>
The head bore a pair of lateral (presumably compound) eyes, with the optic lobes of these extending into the anterior sclerite as a pair of median eye-like frontal organs.<ref name=":3" /> The lateral eyes were originally thought to be dorsal,<ref name=":4" /> but later study suggest it was ventral instead, connected to the anterior sclerite via a pair of short eyestalks.<ref name=":5">{{Cite journal |last=Edgecombe |first=Gregory D. |last2=Ramsköld |first2=Lars |date=1999 |title=Relationships of Cambrian Arachnata and the systematic position of Trilobita |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/relationships-of-cambrian-arachnata-and-the-systematic-position-of-trilobita/208B20094C20C38E688044F130A1CC04 |journal=Journal of Paleontology |language=en |volume=73 |issue=2 |pages=263–287 |doi=10.1017/S0022336000027761 |issn=0022-3360|url-access=subscription }}</ref>
On the underside of ''Kuamaia''{{'}}s head, there is a ventral sclerite (hypostome) connected to the posterior edge of anterior sclerite, located between a pair of antennae. In the case of ''K. lata'', the antennae have paired inner spines, suggesting they were raptorial appendages.<ref name=":3">{{Cite journal |last=O'Flynn |first=Robert J. |last2=Williams |first2=Mark |last3=Liu |first3=Yu |last4=Hou |first4=Xianguang |last5=Guo |first5=Jin |last6=Edgecombe |first6=Gregory D. |date=2025-02-12 |title=The early Cambrian Kuamaia lata, an artiopodan euarthropod with a raptorial frontal appendage |url=https://www.cambridge.org/core/product/identifier/S0022336024000337/type/journal_article |journal=Journal of Paleontology |language=en |pages=1–13 |doi=10.1017/jpa.2024.33 |issn=0022-3360|url-access=subscription |doi-access=free }}</ref> The remaining appendages are numerous pairs of biramous (branched) legs, each compose of a large protopod (base), 5-6 segmented endopod (inner branch) and a flatten exopod (outer branch). The exopods acted as the gills of ''K. lata.''<ref name=":2">{{Cite journal|last1=Suzuki|first1=Yutaro|last2=Kondo|first2=Akiyoshi|last3=Bergström|first3=Jan|date=2008|title=Morphological Requirements in Limulid and Decapod Gills: A Case Study in Deducing the Function of Lamellipedian Exopod Lamellae|journal=Acta Palaeontologica Polonica|volume=53|issue=2|pages=275–283|doi=10.4202/app.2008.0208|issn=0567-7920|doi-access=free}}</ref> These gills were made up of many lamellae, which facilitated gas exchange.<ref name=":2" /><ref>{{Cite web|url=https://www.britannica.com/science/respiratory-system|title=Respiratory system - Gills of invertebrates|website=Encyclopedia Britannica|language=en|access-date=2019-12-05}}</ref> These lamellae were packed together in rows on each exopod. ''K. lata'' had a lower number of these, with an average number of 22 lamellae per exopod, compared to an average of 50 in other arthropods.<ref name=":2" />
Previously the head of this genus were thought to have only 3 pairs of legs,<ref name=":4" /> but later studies on ''K. lata'' revealed 4 pairs instead, suggesting the head was formed by 6 body segments (ocular somite and 5 anterior somites corresponded to the antennae and 4 leg pairs).<ref name=":3" /> Each thoracic segment has 1 pair of legs. The pygidium has 4 pairs of legs in ''K. lata''.<ref name=":5" /><ref name=":3" /> The cephalic and pygidial legs of ''K. muricata'' are unknown, but the pygidium of this species showing traces of 8 body segments, outnumbered those of ''K. lata''.<ref name=":4" /> <gallery mode="packed" heights="250"> File:20250216 Kuamaia lata diagrammatic reconstruction.png|Diagrammatic reconstruction of ''Kuamaia lata'' File:20250219 Kuamaia muricata diagrammatic reconstruction.png|Diagrammatic reconstruction of ''Kuamaia muricata'' </gallery>
== Paleoecology == ''Kuamaia lata'' may had been a benthic arthropod<ref name=":0" /><ref name=":1">{{Cite journal|last1=Zhao|first1=Fangchen|last2=Caron|first2=Jean-Bernard|last3=Bottjer|first3=David J.|last4=Hu|first4=Shixue|last5=Yin|first5=Zongjun|last6=Zhu|first6=Maoyan|date=2014|title=Diversity and species abundance patterns of the Early Cambrian (Series 2, Stage 3) Chengjiang Biota from China|journal=Paleobiology|volume=40|issue=1|pages=50–69|issn=0094-8373|jstor=44017866|doi=10.1666/12056|s2cid=131526964}}</ref> and a mobile predator and scavenger.<ref name=":1" /> The raptorial condition of ''K. lata''<nowiki/>'s antennae are similar to those of ''Kiisortoqia'', suggesting the capability of grasping food items.<ref name=":3" /> A spiny section on ''K. lata''{{'}}s legs is presumed to have allowed it to tear apart food.<ref name=":0" />
== Taxonomy == ''Kuamaia'' is a member of Conciliterga, a subgroup of trilobitomorph artiopods. Within this taxon, It is also classified as helmetiids (Order Helmetiida, Family Helmetiidae) alongside similar forms such as ''Helmetia'', ''Haifengella'' and ''Rhombicalvaria''.<ref>{{Cite journal |last=Zhao |first=Fangchen |last2=Hu |first2=Shixue |last3=Zeng |first3=Han |last4=Zhu |first4=Maoyan |date=2014 |title=A New Helmetiid Arthropod from the Early Cambrian Chengjiang Lagerstätte, Southwest China |url=https://www.researchgate.net/publication/261474798 |journal=Journal of Paleontology |language=en |volume=88 |issue=2 |pages=367–370 |doi=10.1666/13-103 |issn=0022-3360}}</ref><ref name=":3" /> ''Kuamaia'' is distinguishable from other helmetiids by its trapezoid head, 7-8 segmented thorax and relatively reduced lateral spines. ''K. muricata'' is distinguishable from the type species ''K. lata'' by its more thoracic segments, smaller pygidium with more lateral spines, as well as exopod distal segment fringed by bristles.<ref name=":4" />
The derived position of ''K. lata'' within Artiopoda suggest its raptorial antennae were modified from their sensory function in other artiopods, convergent to the ancestrally raptorial frontalmost appendages of other arthropods (e.g. ''Kylinxia'', ''Isoxys'').<ref name=":3" />
Cladogram after Losso et al. 2025:<ref name=":32">{{Cite journal |last=Losso |first=Sarah R. |last2=Caron |first2=Jean-Bernard |last3=Ortega-Hernández |first3=Javier |date=2025-04-04 |title=Helmetia expansa Walcott, 1918 revisited – new insights into the internal anatomy, moulting and phylogeny of Conciliterga |url=https://www.tandfonline.com/doi/full/10.1080/14772019.2025.2468195 |journal=Journal of Systematic Palaeontology |volume=23 |issue=1 |article-number=2468195 |doi=10.1080/14772019.2025.2468195 |issn=1477-2019 |doi-access=free|url-access=subscription }}</ref>{{clade|{{clade |1=''Squamacula'' 80px |2={{clade |1={{clade |1=''Acanthomeridion'' 100px |2={{clade |1=''Zhiwenia'' 50px |2=''Australimicola'' }}}} |2={{clade |1=''Kwanyinaspis'' |2={{clade |1=Vicissicaudata 100px |label2=Trilobitomorpha |2={{clade |1={{clade |1={{clade |1=Xandarellida 100px |2=Nektaspida 100px }} |2={{clade |1={{clade |1=''Retifacies'' 100px |2=''Pygmaclypeatus'' 100px }} |2={{clade |1=''Campanamuta'' |2=Trilobita 100px }}}}}} |label2=Conciliterga |2={{clade |1=''Arthroaspis'' |2={{clade |label1=Tegopeltidae |1={{clade |1=''Skioldia'' |2={{clade |1=''Tegopelte'' 100px |2=''Saperion'' 100px }}}} |label2=Helmetiidae |2={{clade |1='''''Kuamaia lata''''' 100px |2={{clade |1='''''Kuamaia muricata''''' 100px |2={{clade |1=''Helmetia'' 100px |2={{clade |1=''Rhombicalvaria'' |2= ''Haifengella'' }}}}}}}}}}}}}}}}}}}}}}|label1=Artiopoda}}
== References == {{Reflist}}
{{Artiopoda}} {{Taxonbar|from=Q80563553}}
Category:Artiopoda Category:Fossil taxa described in 1987 Category:Artiopod genera