Cretapsaridae Luque, fam. nov, 2021

Luque, Javier, Xing, Lida, Briggs, Derek E. G., Clark, Elizabeth G., Duque, Alex, Hui, Junbo, Mai, Huijuan & McKellar, Ryan C., 2021, Crab in amber reveals an early colonization of nonmarine environments during the Cretaceous, Science Advances 7, pp. 1-13 : 1-2

Cretapsaridae Luque, fam. nov .

LSID. Family group: http://zoobank.org/urn:lsid:zoobank. org:act:81705335-CAED-400E-B1EC-161B56B298AE.

*Corresponding author. Email: [e-mail], [e-mail] (J.L.); [e-mail] (L.X.)

Included genus: Cretapsara Luque , gen. nov., by monotypy.

Diagnosis: As for type genus and species.

†These authors contributed equally to this work.

‡Present address: Florida International University, Biscayne Bay Campus, 3000 NE

Remarks: Cretapsara athanata n. gen. etsp. differsfromanyknown crab family in its combination of plesiomorphic and apomorphic characters. Superficially, itsharessomeresemblancetosomemarineeubrachyuranfamiliessuch as Eogeryonidae, fromthe Upper Cretaceous of Spain [ Eogeryon elegius, Cenomanian ( 14)] ( Fig. 5H ) and the Lower Cretaceousof Brazil [Romualdocarcinus salesi, Albian ( 15)], and Marocarcinidae , fromthe Upper Cretaceousof Morocco [ Marocarcinus pasinii, Cenomanian ( 16)] ( Fig. 5E ). Cretapsara differs from Eogeryonidae and Marocarcinidae in the presenceof a bilobate rostrum and lack of orbital fissures, compared to the bifid and acute rostrum and twowell-developedorbitalfissuresdiagnostic of thesetwofamilies [ Marocarcinidae was initially interpretedas havingnoorbitalfissures due to the erroneous interpretation of the eyestalks as part of the orbit ( 16) but is here recognized as having two orbital fissures and scored as such in our analysis].

The overall carapace outline, the broad front, long legs, and the lack of orbital fissures that characterize C. athanata ( Figs. 1 and 2 ) resemble those of some modern Grapsoidea—a group of highly terrestrial thoracotreme crabscommon in subtidal and supratidal settings worldwide. Despite this, C. athanata differs from grapsoids in important respects. In mostgrapsoids, thereisaconspicuous V-shaped notchbetweenthemerus andischium of thethirdmaxillipeds (mxp3), sothat themandiblesare visible througha large, rhomboidal gapwhen the mxp3 are closed, a featureabsent in Cretapsara ( Figs. 2 , Cand F, and 3, B, E, and G). Moreover, the podomeres of the walking legs in grapsoids, as in most thoracotreme crabs, are subtriangular to flattened in cross section, whereas those in Cretapsara are circular in cross sectionandmoresimilartothoseofotherheterotremes ( Fig.3 ,movieS1, and data file S1). Such similarities between Cretapsara and some grapsoids are likely convergent adaptations to similar ecologies.

Figures

Fig.5.Phylogenetic relationships of Cretapsaraathanata Luque,gen.et sp.nov.inthe crab treeof life. Bayesian majority-rule consensus topology of thepost–burn-in sample of trees for key fossil and extant eubrachyuran families,including probability support values indicated at branches.Branches with posterior probability support <75% are collapsed. Thick solid lines represent the ages of the known first and last occurrences of the studied families. Dotted lines and daggers (†) indicate extinct taxa;solid lines indicate living taxa. Photos: Heikeopsis japonica (A) by T.-Y. Chan; Telamonocarcinus gambalatus (B), M. pasinii (E), and E. elegius (H) by À. Ossó; Archaeochiapasa mardoqueoi (C) by F. Vega; Componocancer robertsi (D) by R.Feldmann and C.Schweitzer; Dilocarcinus septemdentatus (G) and Melothelphusa dardanelosensis (M) by Senckenberg Museum,S.Tränkner,courtesy of C.Magalhães [(M) after (80)]; Cretapsaraathanata Luque gen.et sp.nov.(F)herein;C.maenas (I),C.sapidus(K),Geothelphusa olea (O),Sayamia melanodactylus (P),Geosesarma dennerle (R),and C.guanhumi (S) by O.Radosta;G.trispinosus (J) by C.Noever (CC BY 4.0,https://commons.wikimedia.org/w/ index.php?curid=63236719); Dinocarcinus velauciensis (L) by N. Robin;Potamonauteskunduno (N) by P. Crabb (CC BY 3.0,https://commons.wikimedia.org/w/index.php?curid=29254322);G.cruentata (Q) by A.Anker;and Leptuca oerdesti (T) by J.L. Figure by J.L.

Fig. 1. Cretapsara athanata Luque gen. et sp. nov., a modern-looking eubrachyuran crab in Burmese amber. (A to D) Holotype LYAM-9. (A) Whole amber sample with crab inclusion in ventral view. (B) Close-up of ventral carapace. (C) Whole amber sample with crab inclusion in dorsal view. (D) Close-up of dorsal carapace. White arrows in (B) and (D) indicate the detached left fifth leg or pereopod.Photos by L.X.Figure by J.L.

Fig. 2. Cretapsara athanata Luque gen. et sp.nov. from Burmese amber. (A to G) Detailed views of Holotype LYAM-9.(A) Close-up of antero-ventral carapace with eyes and eyestalks, antennae, and the excurrent openings beside the palps of the third maxillipeds (mxp3).(B) Close-up of dorsal carapace showing the orbits lacking orbital fissures and the anterolateral margin with three spines including the outer orbital spine. (C) Overview of specimen in ventral view with legs,pleon,sternum,mouthparts, eyes,and left cheliped.(D) Close-up of left cheliped in ventral oblique view,showing a straight dactylus and pollex,the latter bearing small acute teeth on occlusal margin. (E) Ventral view of pereopods 2 to 5, showing all legs of similar size and slender shape, with small, thin,spaced setae,and an acute,long dactyli.(F) Close-up of the mxp3, showing the palp and the fine lining of setae in the occlusal margin, the two hollow openings beside the palp of mxp3 (white arrow), and small granulations in the pterygostome. (G) Close-up of posterior sternites and pleon tucked under the carapace, typical of a eubrachyuran. White arrows in (A) and (F) indicate the excurrent openings. an1,antennula; an2,antenna; ce,corneal eye;es,eyestalk; ex,exopod; is, ischium; me,merus; pa:distal palp of mxp3. Photos by L.X.Figure by J.L.

Fig. 3. 3D mesh of Cretapsara athanata Luque gen. et sp. nov. holotype LYAM-9. (A to E) 3D mesh extracted from reconstructed micro-CT data in VGSTUDIO MAX, remeshed in MeshLab, and visualized using Autodesk Maya: (A) dorsal, (B) ventral, (C) right lateral,(D) oblique postero-dorsal,(E) oblique antero-ventral views,showing the claws of equal size and four pairs of slender legs similar in shape and size,with P5 slightly smaller than the other legs.(F and G) Details of the dorsal (F) and ventral (G) carapace,showing details of the large eyes and orbits,small antennae,and a small,acute outer orbital spine [(F) thick arrow],two small anterolateral spines (F,thin arrows), a posterolateral margin bearing at least four small and equidistant tubercles (F,small arrows),straight posterior margin,slender coxae of the pereopods,a typical heterotreme eubrachyuran sternum (G),and a reduced and folded pleon with the first pleonites dorsally exposed.Left fifth pereopod digitally reattached.bcg,branchiocardiac groove; ca,carpus;cg, cervical groove;cx,coxa;da,dactylus;ib,ischiobasis;ma,manus or palm of claw;P1,claws or chelipeds;P2 to P5,pereopods or walking legs 2 to 5; po,pollex or fixed finger cheliped propodus; pr,propodus.Images by E.G.C. Figure by J.L.