Nov 27, 2008 - Cryptorhynchia Buckman, 1917 is another such fleeting genus which was known until recently to have existed only during the late. Bathonian.
This article was downloaded by: [University of South Florida] On: 26 April 2013, At: 02:18 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Alcheringa: An Australasian Journal of Palaeontology Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/talc20
Significance of new species of Cryptorhynchia (Brachiopoda) from the Middle Jurassic of Kutch, India Debahuti Mukherjee Ghosh
a b
a
, Subhendu Bardhan & Diptendu N.
c
a
Department of Geological Sciences, Jadavpur University, Calcutta, 700032, India E-mail: b
Palaeontology Division 1, Geological Survey of India, 15A-B Kyd Street, Calcutta-16, India c
Indian School of Mines, Dhanbad, 826 004, India Version of record first published: 27 Nov 2008.
To cite this article: Debahuti Mukherjee , Subhendu Bardhan & Diptendu N. Ghosh (2002): Significance of new species of Cryptorhynchia (Brachiopoda) from the Middle Jurassic of Kutch, India, Alcheringa: An Australasian Journal of Palaeontology, 26:2, 209-231 To link to this article: http://dx.doi.org/10.1080/03115510208619253
PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/terms-andconditions This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Significance of new species of Cryptorhynchia (Brachiopoda) from the Middle Jurassic of Kutch, India DEBAHUTI MUKHERJEE, SUBHENDU BARDHAN AND DIPTENDU N. GHOSH
Downloaded by [University of South Florida] at 02:18 26 April 2013
MUKHERJEE,D., BARDHAN,S. & GHOSH,D. N., 30.5.2002. Significance of new species of Cryptorhynchia (Brachiopoda) from the Middle Jurassic of Kutch, India. Alcheringa 26, 209-231. ISSN 0311-5518. Cryptorhynchia is a brachiopod genus, until recently known only from the late Bathonian. Two new species C. karuna and C. jhooraensis are here described from the middle Bathonian at Kutch, western India and record the earliest known occurrences of the genus. They constitute ancestor-descendant lineages with the two existing younger species C. pulcherrima and C. rugosa respectively. Evolution in both cases shows 'parallel' trends and the descendants are scaled-down versions of their respective progenitors. Statistical analyses reveal that this evolutionary miniaturization involves allometry-induced heterochrony, especially progenesis, and is marked by a rapid speciation event compatible with the punctuational model. Evolution appears to be anagenetic and may be attributed to the unstable nature of environment where onshore innovation produced smaller descendants that adopted r-strategy. Facies distribution and functional morphology suggest that species of Cryptorhynchia were well adapted to shallow, unstable carbonate shelf. However, they disappeared suddenly at the Bathonian - Callovian boundary which was marked by a global transgression. The possible causal factors of their extinction may be the consequent changes in bathymetry and substrate condition. D. Mukherjee* [debahutim@hotmaiLcom] & S. Bardhan, Department of Geological Sciences, Jadavpur University, Calcutta 700032,India; D.N. Ghosh, Indian School of Mines, Dhanbad 826 004, India; *present address: Palaeontology Division 1, Geological Survey of lndia, 15A-B Kyd Street, Calcutta-16, India; received 14.8.2000, revised 30.5.2001. Keywords: Cryptorhynchia, Bathonian, evolution, heterochrony, progenesis. MANY BRACHIOPOD GENERA, particularly in the Mesozoic, appeared cryptogenetically, and show wide b i o g e o g r a p h i c distribution, often spreading across continents or faunal provinces. T h e y are m o r p h o l o g i c a l l y very distinct with individual species marked b y low intraspecific variability, exhibiting little or no change due to geographic variation. For example, Flabellothyris dichotoma Kitchin, 1900 which existed only during the late Bathonian, has been recorded from Mexico, Morocco and India (Ager & W a l l e y t977). Ager (1984, 1986) described many such genera, which lasted very briefly and left no obvious ancestors or descendants. Because o f their n a r r o w t e m p o r a l and wide g e o g r a p h i c 0311/5518/2002/01209-23
$3.00
© AAP
dispersion, Ager (1984) aptly designated them as'fleeting taxa'. Cryptorhynchia Buckman, 1917 is another such fleeting genus w h i c h was k n o w n until recently to have existed only during the late Bathonian. It includes species from E u r o p e ( B u c k m a n 1917, Shi & Grant 1993), P a m i r (Ovcharenko 1983), China, New Zealand (Shi & Grant 1993), India (Kitchin 1900, Buckman 1917, Mitra & Ghosh 1973), Burma (Buckman 1917) and North America (Perry 1979) (Fig. 1), thus cutting across the boundaries o f several faunal provinces. The genus shows low diversity and some species are barely distinguishable and may be conspecific. H o w e v e r , t w o w e l l - k n o w n s p e c i e s , C. pulcherrima Kitchin, 1900 (the type species), and
210
AL CHERINGA
MUKHERJEE, BARDHAN AND GHOSH
RA N N OF KUTCH
Is tand
,0023,,~ •
Downloaded by [University of South Florida] at 02:18 26 April 2013
"'~X~I
GULF OF KUTC~.~../
Fig. 2. Geographic localities with studied area and map of the Jurassic (dotted regions) of Kutch, India. Inset shows the position of Bhuj, the district town of Kutch, and Mumbai.
Fig. 1. Distribution of Cryptorhynchia during the late Bathonian; paleocontinental reconstruction, modified after Enay & Cariou (1997).
C. rugosa Kitchin, 1900, withstood close scrutiny and lived side b y side t h r o u g h o u t their stratigraphic range in Kutch, India, during the late Bathonian (Ghosh 1967, Mukherjee & Ghosh 2000). C. pulcherrima was also reported from the coeval horizon in Pamir (Ovcharenko 1983), suggesting rapid migration. The existence o f a seaway is evident from the occurrence of common ammonite taxa such as Bullatimorphites Roemer, 1911 and Sieimiradzkia Hyatt, 1900 (Arkell 1956, p. 403; Pandey & Westermann 1988; Jain et al. 1996) and other brachiopod lineages such as Kutchithyris
acutiplicata-K,
euryptycha
(Kitchin, 1900) (see Ovcharenko 1969). Here we d e s c r i b e two n e w species o f Cryptorhychia f r o m the middle B a t h o n i a n horizons underlying the pulcherrima-rugosa beds. If the age assignment is correct, they represent the oldest k n o w n Cryptorhynchia. They are larger than any known species o f the genus and are named Cryptorhynchia karuna and C.jhooraensis. Detailed statistical analyses and other evidence reveal that C. puleherrima and C. rugosa correspond closely to the young
C. karuna and C. jhooraensis respectively. Thus it a p p e a r s that e a c h pair c o n s t i t u t e s an evolutionary ancestor-descendant lineage. E v o l u t i o n in b o t h the cases i n v o l v e s paedomorphosis, progenesis in particular, with d e s c e n d a n t species b e c o m i n g smaller and retaining the early morphological traits o f the progenitor (cf. Gould 1977, McNamara 1986). This allometry-induced heterochronic evolution is attributed to the unstable environment where onshore innovation (cf. Jablonski et aL 1983) produced descendants that opted for r - selected regime. Speciation was rapid, prompted by p a e d o m o r p h i c m e c h a n i s m and left no intermediate forms. This is compatible with the punctuational model o f evolution (sensu Gould & Eldredge 1977, 1993). In each evolutionary plexus, the ancestor has been succeeded by the d e s c e n d a n t . A n a r r o w h o r i z o n m a r k s the coincidence o f ancestor and descendant thus constituting a slight overlap in stratigraphic distribution, so it appears that the ancestor did not survive long after speciation. Cryptorhynchia disappeared all over the world at the top of the late Bathonian but, in most cases, precise stratigraphic positions are not clear. It is shown in Kutch that they became extinct precisely
Fig. 3. Stratigraphic sections at (A) Jumara (modified after Bardhan et al. 1994) and (B) Jhura showing the range of the two new species of Cryptorhynehia and the distribution of C. pulcherrima, C. rugosa and some key ammonite taxa. 1. Greyish yellow limestone with Golden oolite alternation. 2. Cream/white/grey limestone. 3. Golden oolitic limestone and shale alternation. 4. Slabby limestone/shale alternation. 5. Cream limestone/coral biostmme alternation. 6. Green oolitic limestone. 7. Yellow/grey / white shelly limestone and shale alternation.
ALCHERINGA
MIDDLE JURASSIC CR YPTORHYNCHIA FROM INDIA
B
Units
211
A 187 m
-I-I
°~
Z
I
-I-~
-5-i--i:-] 1 I II
