Thoracotremata

{{Automatic taxobox

| image = Purple rock crab444.jpg

| image_caption = Leptograpsus variegatus, Grapsidae

| taxon = Thoracotremata

| authority = Guinot, 1977

| subdivision_ranks = Families

| subdivision = See text

}}

Thoracotremata is a clade of crabs, comprising those crabs in which the genital openings in both sexes are on the sternum, rather than on the legs. It comprises 17 families in four superfamilies .{{cite journal |journal = Raffles Bulletin of Zoology |year=2009 |volume = Suppl. 21 |pages=1–109 |title = A classification of living and fossil genera of decapod crustaceans |author1=Sammy De Grave |author2=N. Dean Pentcheff |author3=Shane T. Ahyong |url=http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf|display-authors=etal}}

Evolution

Thoracotremata is the sister group to Heterotremata within the clade Eubrachyura, having diverged during the Cretaceous period. Eubrachyura itself is a subset of the larger clade Brachyura, which consists of all "true crabs". A summary of the high-level internal relationships within Brachyura can be shown in the cladogram below:

{{cite journal |title=Evolutionary History of True Crabs (Crustacea: Decapoda: Brachyura) and the Origin of Freshwater Crabs |author1=Ling Ming Tsang |author2=Christoph D. Schubart |author3=Shane T. Ahyong |author4=Joelle C.Y. Lai |author5=Eugene Y.C. Au |author6=Tin-Yam Chan |author7=Peter K.L. Ng |author8=Ka Hou Chu |journal=Molecular Biology and Evolution |publisher=Oxford University Press |volume=31 |issue=5 |year=2014 |pages=1173–1187 |doi=10.1093/molbev/msu068 |doi-access=free|pmid=24520090 }}{{cite journal |last1=Wolfe |first1=Joanna M. |last2=Breinholt |first2=Jesse W. |last3=Crandall |first3=Keith A. |last4=Lemmon |first4=Alan R. |last5=Lemmon |first5=Emily Moriarty |last6=Timm |first6=Laura E. |last7=Siddall |first7=Mark E. |last8=Bracken-Grissom |first8=Heather D. |title=A phylogenomic framework, evolutionary timeline and genomic resources for comparative studies of decapod crustaceans |journal=Proceedings of the Royal Society B | date=24 April 2019 |volume=286 |issue=1901 |doi=10.1098/rspb.2019.0079|pmc=6501934 |pmid=31014217 |doi-access=free }}

{{clade| style=font-size:85%; line-height:85%

|label1=Brachyura

|1={{clade

|1=Dromiacea

|2={{clade

|1={{clade

|1=Raninoida

|2=Cyclodorippoida }}

|label2=Eubrachyura

|2={{clade

|1=Heterotremata

|2=Thoracotremata }} }} }} }}

The internal relationships within Thoracotremata are less certain, with many of the superfamilies found to be invalid. The proposed cladogram below is from analysis by Tsang et al, 2014:

{{clade| style=font-size:85%; line-height:85%

|label1=Thoracotremata

|1={{clade

|1=Pinnotheridae

|2=Dotillidae }}

|2={{clade

|1=Percnidae

|2={{clade

|1={{clade

|1=Xenograpsidae

|2=Cryptochiridae }}

|2={{clade