EKALAKIA LAMBERTI N. GEN., N. SP. (CRUSTACEA, DECAPODA) FROM THE UPPER CRETACEOUS

PIERRE SHALE OF EASTERN MONTANA

G A L E A . B I S H O P

Reprinted from J O U R N A L OF PALEONTOLOGY

Vol. 50, No. 3, May 1976 pp. 398^01

Made in United States of America Copyright © 1976, The Society of Economic Paleontologists and Mineralogists

398 GALE A. BISHOP

J O U R N A L OF PALEONTOLOGY, V. 5 0 , NO. 3, P. 3 9 8 - 4 0 1 , 1 PL., 1 TEXT-FIG. , M A Y 1 9 7 6

EKALAKIA LAMBERTI N. GEN., N. SP. (CRUSTACEA, DECAPODA) FROM THE UPPER CRETACEOUS

PIERRE SHALE OF EASTERN MONTANA

G A L E A . B I S H O P Depa r tmen t , of Geology, G e o r g i a S o u t h e r n College, S t a t e s b o r o , G e o r g i a 30458

ABSTRACT—Ekalakia lambcrti n. gen., n. sp. is r e p r e s e n t e d by t w o spec imens f r o m e a s t e r n M o n t a n a . B o t h w e r e col lected f r o m the P i e r r e S h a l e of L a t e C r e t a c e o u s ( C a m p a n i a n or M a a s t r i c h t i a n ) age . T h i s t a x o n e n l a r g e s o u r k n o w l e d g e of t he M e s o z o i c D r o m i o i d e a .

I N T R O D U C T I O N

FO S S I L crabs are r a re in Cretaceous rocks.

T h e discovery of two specimens of Eka-lahia n. gen. demons t ra tes the presence of the Prosopidae in the La te Cretaceous of Mon-tana. Exac t s t ra t ig raphic and geographic da ta are lacking fo r the two specimens which were graciously loaned to me by Mr . Marshal l Lambert , Cura to r of the Car te r County Museum (C.C.M.) fo r examinat ion and description.

Specimen C.C.M. 5590 was collected by Marshal l Lamber t f r o m the P i e r r e Shale "about 30 miles south of Eka laka in T . 4 S., R. 60E., probably in section 1 or 12." Th i s locality is in the headwate r s of Skull Creek, a t r ibu ta ry of Boxelder Creek, Car t e r County, Montana . Specimen C.C.M. 5571 was collected f r o m the P ie r r e Shale "southeast of Baker , Montana , by the late Alber t F o s t . . . in 1950." Th i s de-scription indicates the locality is on the str ike of the axis of the Cedar Creek Ant ic l ine which br ings the uppermost P i e r r e Shale to the sur-face along its crest (Dobbin and Larsen , 1934). T h e uppermost P i e r r e Shale in this a rea is probably Campanian or possibly Maas t r i ch t i an in age (Bishop, 1973a; Robinson, Mapel, and Cobban, 1959, p. 103; Gill and Cobban, 1973, p. 25) .

T h e scarcity of fossil crabs f r o m most of the Cretaceous of Nor th Amer ica places these specimens in a position of importance. The re -fo re it was deemed use fu l to publish this note even though exact s t ra t ig raphic or geographic

in fo rmat ion is lacking on each specimen. Th i s c rab adds to our previous knowledge of the b rachyuran decapod f a u n a of the P i e r r e Shale in the W e s t e r n In te r io r which consists o f :

Dakoticanccr over anus Rathbun, 1917 Homolopsis punctata Ra thbun, 1917 Nccrocarinus picrrcnsis ( R a t h b u n ) , 1917 Tctracarcinus subquadratus Wel ler , 1905 Homolopsis daivsoncnsis Bishop, 1973 Ekalakia lambcrti n. gen., n. sp.

T h e f i rs t th ree species very o f t e n occur to-ge ther in g rea t numbers as recognizable as-semblages (Bishop, 1972). T h e other t a x a oc-cur as single specimens in widely separa ted a reas ( T . subquadratus, one specimen, W y o -m i n g ; H. daivsoncnsis, one specimen, near Glendive, M o n t a n a ; and E. lambcrti, twro speci-mens, Car t e r County, M o n t a n a ) .

S Y S T E M A T I C P A L E O N T O L O G Y

Super fami ly D R O M I O I D E A de H a a n , 1833 Fami ly P R O S O P I D A E von Meyer , 1860

Subfami ly P R O S P O P I N A E von Meyer, 1860 Genus E K A L A K I A n. gen.

Type spccics.—Ekalakia lambcrti n. sp. f r o m the Upper Cretaceous P ier re Shale of eas tern Mon tana .

Etymology.—From the nearby communi ty of Ekalaka , Montana .

Diagnosis.—Carapace slightly longer than wide wi th f l a r i ng rec tangula r an ter ior pro-t rud ing ahead of the ovate, nearly circular

< -

E X P L A N A T I O N OF P L A T E 1

FIG. 1-1—Ekalakia lambcrti n. gen., n. sp., h o l o t y p e ( C . C. M . # 5 5 9 0 ) in 7, d o r s a l v i ew ( X l ) ; 2, do r sa l v iew ( X 2 ) ; 3, a n t e r i o r v i ew ( X 2 ) ; a n d 4, r i g h t l a t e ra l v i ew ( X 2 ) .

5 — E k a l a k i a lambcrti n. gen., n. sp., p a r a t y p e ( ( ' . C. M . # 5 5 7 1 ) in d o r s a l v i ew ( X l ) -6—Stipple d r a w i n g of Ekalakia lambcrti 111 d o r s a l v i ew ( X 8 ) .

Copyright © 1976, The Society of Economic 3 9 9 Paleontologists and Mineralogists

400 GALE A. BISHOP

T K X T - K K ; . /—likalakia lamberti, dorsal view, ing terminology.

show-

Regions EG MSG MTG 1'G 11 BA IiM i n u c i

epigastr ic n a s o g a s t r i c metagas t r ic pro togas t r ic hepatic anter ior braneliial mesohranchial nictabranchial u rogas t r ic cardiac intestinal

Grooves : e cervical a branchio-card iac b an tennular ae a t tachment of the

at tractor cpimcralis muscle

poster ior . Ca rapace s t rongly convex t r ans -versely and convex longitudinal ly. Cervical and b ranch io -ca rd iac f u r r o w s U-shaped , equally deep, and subparal lel . T h e s e a long wi th a weak, subparal lel , U- shaped depress ion be tween the epigast r ic and p ro togas t r i c reg ions and a change in slope onto the shelf - l ike pos ter ior , s epa ra t e the ca rapace into f ive U- shaped bands. Ros-t rum d o w n t u r n e d wi th well de f ined medial sulcus.

Comparison.—The paral lel , equally developed, U-shaped cervical and b ranch io -ca rd iac f u r -rows help to d is t inguish this genus f r o m the o ther prosoponopids . I t is s imilar in shape to Prosopon von Meyer , 1835, Lacviprosopon Glaessner , 1933, l^cctis W i t h e r s , 1945, and Wihningtonia W r i g h t and Collins, 1972. Eka-lakia has a s t r a igh te r b ranch io -ca rd iac f u r r o w wi th no f o r w a r d convexi ty as is shown by Prosopon, Laci'iprosopon, and Vcctis. In over -

all shape and aereo la t ion Ekalakia is most similar to Wihningtonia f r o m which it can be d is t inguished by its m o r e oval shape, n a r -r o w e r scapular arch , m o r e subdued aereola t ion , and much less developed a n t e r i o r - b r a n c h i a l bosses.

E K A L A K I A L A M B E R T I n . s p .

PI. 1, f igs . 1 - 6 ; T e x t - f i g . 1

Etymology.—In honor of the collector of the holotype, Marsha l l E. L a m b e r t , C u r a t o r of the C a r t e r Coun ty Museum, Ekalaka , Mon-tana .

Types.—The holotype (C.C.M. #5590) and pa ra type (C.C.M. #5571) a re deposi ted in the collections of the C a r t e r County Museum in Eka laka , M o n t a n a .

Occurrcncc.—The t w o specimens of Ekalakia lamberti a r e decor t i ca ted s t e inke rns p r e s e r v e d in d a r k g r a y l imestone concre t ions a long wi th m a n y molluscs. T h e c a r a p a c e was appa ren t ly th in ~ 0.3 m m ) and peeled o f f as the speci-mens w e r e p repa red . Some sc ra tch m a r k s f r o m the p r epa ra t i on a re obvious on both specimens. Both specimens a r e f r o m the P i e r r e Sha le of U p p e r Cre t aceous ( C a m p a n i a n or pe rhaps M a -a s t r i c h t a n ) age.

Description.—The c a r a p a c e ( T e x t - f i g . 1) is oval wi th a p r o t r u d i n g an te r io r , s l ightly longer t han wide, and widest ac ross the mesohranch ia l region. I t is convex longi tudinal ly and ve ry convex t r ansve r se ly .

C.C.M. #5590 C.C.M. #5571

Leng th , m m 10.7 14.7

W i d t h , m m 9.3

12.6

T h e c a r a p a c e is crossed by t w o equally de-veloped deep t r a n s v e r s e g rooves tha t a re sub-paral lel to one ano the r and U-shaped . T h e an te r io r one is the cervical g roove . T h e pos-te r io r one, the b ranch io-ca rd iac , is s t r a i gh t e r across the bot tom of the " U " with sl ightly angu la t ed junc t ions wi th the a r m s of the " U . " In these bends t h e r e m a y be small pits developed. A th i rd U - s h a p e d g roove is a poor ly developed depress ion t h a t lies an t e r io r to the cervical g roove and sepa ra t e s the ep igas t r ic and mesogas t r i c a r ea s f r o m the p r o t o g a s t r i c and m e t a g a s t r i c a reas . A medial ros t ra l sulcus is well developed on the ro s t rum and splits in to f a i n t e r g rooves on e i ther side of the meso-gas t r i c and me tagas t r i c a r ea s becoming bare ly d iscernable be tween the cervical and b ranch io -card iac f u r r o w s . A very fa in t g roove ( t h e a n t e n n u l a r f u r r o w ) splits o f f the cervical f u r -row n e a r the ou te r edge of the dorsa l shield

CRETACEOUS DROMIOfl) CRAB 401

and extends fo rwa rd . Opposi te the point whe re the hranchio-cardiac f u r r o w bends, a b ranch of the branchiocard iac extends backward and inward diminishing in depth until it d isappears near the cardiac region. Bet te r def ined along the edges of the cardiac region is the a t tach-ment scar of the attractor epimcralis muscle. T h e hranchio-card iac f u r r o w becomes only a change in slope along the poster ior of the car-diac area. A change in cu rva tu re of the cara -pace divides the metabranchia l region into two par t s just behind the cardiac region. Th i s change in slope is more prominent on the smaller specimen.

The regions are thus d i f f e r en t i a t ed into f ive U-shaped bands with the U ' s opening anter ior ly . T h e f i rs t band, ahead of the slight depression, consists of the t r i angu la r n a s o g a s t r i c and a pair of roughly t r i angu la r epigastr ic areas . T h e anter ior of the la t ter merge f o r m i n g the sulcate, downturned ros t rum. A pair of low epigastr ic ridges parallel the gas t r ic f u r r o w s f r o m the rostra l a rea near ly to the depression. T h e second band consists of the medial, hexagona l metagas t r ic region bounded by paired proto-gast r ic regions which are produced distally into prominent , vertical , hepat ic bosses. T h e th i rd band is a cont inuous r idge barely separated into a medial u rogas t r i c region bounded by the paired anter ior branchia l regions. T h e four th band is the broadest and consists of the cardiac mesobranchial , and inf la ted pa r t of the meta-branchial regions. T h e cardiac region is raised well above the rest of the carapace. T h e f i f t h band f o r m s a broad shelf on the hind marg in of the carapace and consists of the intest inal and paired, f la t tened, poster ior par t s of the metabranchia l regions. A very fa in t poster ior margina l groove is present a long the r a the r s t ra ight poster ior margin .

T h e slightly unde r tu rncd lateral marg in is crossed by three grooves. T h e deep gas t r ic de-pression and cervical groove a re bent backward and the less distinct h ranchio-card iac f u r r o w curves f o r w a r d to meet the cervical . T h e r e is a slight r idge on the an te r ior branchia l region just behind the cervical f u r r o w .

A C K N O W L E D G M E N T S

I would like to ex tend my gra t i tude to Marshal l Lamber t fo r loaning the specimens to me for this s tudy and to M y r a ITollaclay and Sue Colson of the Depa r tmen t of Geology, Georgia Sou thern College f o r typing the manu-script. Re inhard Fo r s t e r of the Bayer ische

S taa t s sammlung f u r Pall iontologie und his-tor ische Geologie and J . Dale Na t ions of Nor th -ern Ar i zona Univers i ty read the manuscr ip t and o f f e r e d many valuable suggest ions. Th i s study was in par t made possible by cont inuing support of the Facul ty Research Committee at Georgia Sou thern College.

R E F E R E N C E S

Bishop, G. A. 1972. P r e s e r v a t i o n of fossi l c rabs I rom the Dakoiicanccr Assemblage , U p p e r Cre-taceous P i e r r e Shale, S o u t h D a k o t a . Georg ia Acadenry Science Bull. ( A b s t . ) . 3 0 ( 2 ) :80.

. 1973a. B i o s t r a t i g r a p h i c m a p of the n o r t h end of the Ceda r Creek Antic l ine , D a w s o n Co., M o n t a n a . Mon t . Bur . Alines and Geol. Spec. Pub . 01 : l -2 , map.

. 1973b. 1 fiunolopsis dazcsancusis : A new crab (Crus t acea , D e c a p o d a ) f r o m the P i e r r e Sha le ( U p p e r Cre taceous , M a a s t r i c h t i a n ) of Cedar Creek Antic l ine , eas t e rn M o n t a n a . J o u r . Pa leon to logv . 4 7 ( 1 ) : 19-20, pl. 1.

Dobbin, C. E., and R. M. La r sen . 1934. Geologic and s t r u c t u r e con tour m a p of the S o u t h e r n half of the Cedar Creek Antic l ine , Fa l lon Count}', Mon tana , and B o w m a n County , N o r t h Dako ta . U . S . Geol. Su rv . Genera l M i n e r a l Resources Map .

Gill, J . R., and \V. A. Cobban. 1973. S t r a t i g r a p h y and geologic h i s to ry of the M o n t a n a G r o u p and equivalent rocks, M o n t a n a , W y o m i n g , and N o r t h and S o u t h D a k o t a . U . S . Geol. Su rv . P r o f . P a p e r 770 :1—37.

Glaessner , M. E. 1909. Decapoda , in T r e a t i s e on I n v e r t e b r a t e Pa leon to logy , R. C. M o o r e ( ed . ) , P a r t R. A r t h r o p o d a 4, ( 2 ) . Lawrence , Kansas , T h e U n i v e r s i t y of K a n s a s and Geol. Soc. A m e r i c a .

H a a n , W . de. 1883-50. Crusfacca: in Siebold, P . F., F a u n a J a p a n i c a sive descr ip to animal ium, quae in i t inere per J a p a n i a m , jus su et auspiciis super -iorum, qui s u m m u m in India , B a t a v a I m p e r i u m tenent, suscepto, annis 1823-30 collegit, notis, observat ioni lms, et adumbra t ion ibus I X - X V I , I -X X X I , V I I X V I I . 1 - 2 4 3 p . , p i s . 1, 2 .

Meyer , I I . von. 1800. D ie P r osopon idenode r die Eami l ie der Maskendrebse . Pa l aeon tog raph ica . 7 : 183-222, pl. 23.

Ra thbun , M. J . 1917. N e w species of S o u t h D a -ko ta Cre taceous crabs. U . S . N a t . Mus . P roc . 52:385-391, pl. 32, 33.

. 1935. Fossil C r u s t a c e a of the At l an t i c and Gulf Coasta l Pla in , Geol. Sc. A m e r . Spec. P a p e r 2, 1 0 0 p .

Robinson, C. S., W . J . Mapel , and W . A. Cobban. 1959. P i e r r e Sha l e a long wes t e rn and n o r t h e r n f l anks of Black Hi l l s , W v o m i n g and Mon tana . A m e r . Assoc . Pe t . Geol. Bull . 4 3 ( 1 ) :101-123.

Wel le r , S t u a r t . 1905. T h e f a u n a of the C l i f f -w o o d ( N T . ) Clavs. Jou r . Geologv, 1 3 ( 4 ) :324-337.

W r i g h t , C. W. , and J . S. H . Collins. 1972. Br i t -ish Cre taceous Crabs . Pa l aeon tog raph i ca l Socie ty Mon . 114 p , 22 pis.

M A N U S C R I P T RECEIVED A U G U S T 12 , 1 9 7 4 R E V I S E D M A N U S C R I P T RECEIVED A P R I L 10 , 1 9 7 5

Georg ia S o u t h e r n College cont r ibu ted $75 t o w a r d publ icat ion of this paper .