Dromiacea

{{Short description|Group of crabs}}

{{Automatic taxobox

| fossil_range = {{fossil_range|Jurassic|Recent|earliest=Mississippian}}

| image = Sponge crab eating a sea urchin.jpg

| image_caption = Dromia dormia (Dromioidea: Dromiidae) feeding on a sea urchin

| taxon = Dromiacea

| authority = De Haan, 1833

| subdivision_ranks = Superfamilies

| subdivision =

• Dakoticancroidea †
• Dromioidea
• Glaessneropsoidea †
• Homolodromioidea
• Homoloidea

}}

Dromiacea is a group of crabs, ranked as a section. It contains 240 extant and nearly 300 extinct species.{{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 |url-status=dead |archiveurl=https://web.archive.org/web/20110606064728/http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf |archivedate=2011-06-06 }} Dromiacea is the most basal grouping of Brachyura crabs, diverging the earliest in the evolutionary history, around the Late Triassic or Early Jurassic. Below is a cladogram showing Dromiacea's placement within Brachyura:

{{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 larvae of Dromiacea resemble those of the Anomura more closely than those of other crabs.{{Citation needed|date=May 2021}} This may simply reflect their basal position in the crab phylogeny. The superfamily Eocarcinoidea, containing Eocarcinus and Platykotta, was previously considered to be a member of the Dromiacea, but has since been transferred to the Anomura.{{cite journal |author1=Jérôme Chablais |author2=Rodney M. Feldmann |author3=Carrie E. Schweitzer |year=2011 |title=A new Triassic decapod, Platykotta akaina, from the Arabian shelf of the northern United Arab Emirates: earliest occurrence of the Anomura |journal=Paläontologische Zeitschrift |volume=85 |issue=1 |pages=93–102 |doi=10.1007/s12542-010-0080-y |bibcode=2011PalZ...85...93C |url=http://decapoda.nhm.org/pdfs/31744/31744.pdf }}

The fossil record of Dromiacea reaches back at least as far as the Jurassic,{{cite journal |title=On the influence of fishes on the evolution of benthic crustaceans |author=J. W. Wägele |journal=Journal of Zoological Systematics and Evolutionary Research |date=2009 |volume=27 |issue=4 |pages=297–309 |doi=10.1111/j.1439-0469.1989.tb00352.x|doi-access=free }} and, if Imocaris is indeed a member, into the Carboniferous.{{cite journal |author=Frederick Schram & Royal Mapes |year=1984 |title=Imocaris tuberculata, n. gen., n. sp. (Crustacea: Decapoda) from the upper Mississippian Imo Formation, Arkansas |journal=Transactions of the San Diego Society of Natural History |volume=20 |issue=11 |pages=165–168}}

Dromiacea primarily consists of two groups of superfamilies - Dromioidea and Homoloidea. See the below cladogram:

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

|label1=Dromiacea

|1={{clade

|label1=Dromioidea

|1={{clade

|1=Dromiidae (may be paraphyletic)

|2=Dynomenidae }}

|label2=Homoloidea

|2={{clade

|1=Homolidae (paraphyletic)

|2=Latreilliidae }} }} }}

Recent studies have found that some of the families may not be monophyletic, but rather paraphyletic.

• The Dromioidea family Dromiidae may be paraphyletic with respect to Dynomenidae
• The Homoloidea family Homolidae is paraphyletic with respect to Latreilliidae