CHAPTEi: Y
FAMILY : PACHYDISCIDAE CHAPTER V
The family Pachydlscldae Is fairly abundant in rocks of
South Indian Cretaceous. No representative of It Is found in the rocks of Utatur Group, Though known to have appeared in Upper Alblan, in this region this family seems to have existed from Turonian onwards.
Of the four genera Lewesiceras. Pseudo.lacobites,
Nowakites and Anapachydlscus representing this family in the present collection the genus Lewesiceras is widespread and abundant in rocks of Lower Trlchinopoly Group. The species
Leweslcaras va.ju is collected from Lower Trlchinopoly near a Sattanur, Sara^angalam; and Sastrl ^ al^ (1968) finding It characteristic of lowermost horizon of the Trlchinopoly formation have named It as Lewerlceras va.ju zone. Besides
South India this species is reported from rocks of Turonian age
In Palestine (H. Taubehans, 1920). The other two species of
Leweslc^ras peramplus (Mantell) and Lewesiceras anapadense
(Kossmat) occur in the same horizon as Lewesiceras va.ju. Emil
Bose (1918) has mentioned the presence of this species frdrn uo
Lower Turonian of Portugal, Algeria, Tunisia, North Africa,
C.W.Wright and E.W.Wright (1950) have recorded this species in Turonian of the Chalk of Great Britlan.
- 96 - - 97 -
The genus Pseudo.jacobltes Is not so abundant as
Lewesiceras and its two species PseudoJacobltes rotallnus
(Stollczka) and Pseudo.lacobltes gharel sp. nov . are collected from Sattanur in association with Lewesiceras va.ju and
Lewesiceras peramplus. The genus Pseudo.lacobites is reported from Upper Turonlan of Japan and South England.
Nowakltes .limboi (Kossmat) and Nowakites badwei sp. nov. come from rocks of Trlchinopoly Gronp, Saradmangalam in s association with Mesopuzosia and Pachydegmoceras. Besides
South India Nawakites .jimboi is reported from Santonian of
Madagascar by Colllgnon (1966).
Anapachydiscus ariyaloorensis Stoliczka is the only species in our collection which represents the family
Pachydiscidae in the Ariyalur group. Our specimens come from gritty limestones at Mettal and Maloor of Lower Ariyalur Group
(Sillakudi Formations). Outside South India it is reported from the rocks of Campanian age of Madagascar vCollignon, 1933)
Family s Pachydiscidae Spath, 1922 Genus ; Lewesiceras Spath, 1939
Lewesiceras peramplus (Mantell) (PI. XXXVII, Figs. 1 to 6 ; Text Figs. 143 to 146 ) 1865 Ammonites peramplus Mantell : Stoliczka, p. 130, pi. LXVI, Fig. 2. PL U V '
- 98 -
1939 Leweslceras perainplus (Mantell) : Spath,
Material ; Five specimens.
Plesiotvpe : MACS G 1361 -
Measureme nts ;
No, : b/h ; u/d
MACS G 1361 1.35 0.34 MACS G 1362 1.30 0.33 MACSG 1363 1.28 — MACS G 1364 1.24 0.33 MACSG 1365 1.28 -
Description ; Fairly evolute, tumid shell with a depressed whorl section, broader then high, a broadly rounded semicircular venter,^ con vex whorl bides; subroutided umbilicsl shoulder; nearly vertical uuibilical wall; fairly deep umbilicus.
Last whorl sho'.vs five to six progressively prorsoradiate constrictions, projected over the venter; the inner bordering rib oi‘ the constriction starts from an elongated tubercle.
Ribs between consecutive constrictions varying from three to ten, variable in length but generally long and short alternating, progressively prorsoradiate, projected over the venter and parallel to the constrictions.
Remarks ; In the description of Ammonites peramplus, Stoliczka has described this species to Include the bltuberculate shells - 99 -
along with those having only umbilical tubercles. But
Kossmat separated the bituberculate shells as a distinct Iccs5tvia+ species named Pachydiscus anapadense; sOj'the shells with only
one set of tubercles (umbilical) are taken here to belong to
Lewesiceras peramplus (Mantell).
Occurrence i All our specimens come from limestones of
Trichinopoly Group at Saradamangalam.
Distribution ; Emil Bose (1918) has mentioned the presence of
this species from Lower Turonian of Portugal, Algeria and
Tunisia (North Africa). C. W. Wright and E. W. Wright (1950)
have recorded this species in Turonian of the Chalk of
Great Britain,
Levtesiceras anapadense (Kossmat)
( PI. XXXVIII, Figs. 1, 2, 3; Text Figs. 147, 148, 149 )
1865 Amuonites peramplus Mantell ; Stoliczka, p. 130, pi. LXV, Fig. 1 (non-fig. 2).
1897 Pachvdiscens oiutpadenae Kossraat : Kossmat, p. 90, Taf. XIV (XX), Fig. 2.
Material : Five specimens.
Piesiotype : MACS G 1366 ,
Measurements ; K8 - 100 -
N o . : b/h ; u/d
MACS G 1366 1.40 0.35 MACS G 1367 1,35 0.34 MACS G 1368 1.40 MACS G 1369 1.39 0.33 MACS G 1370 1.41 0.35
Description ; Fairly evolute and tumid shell, with a
depressed whorl section; a broadly rounded semicircular venter, convex whorl sides, subrounded umbilical shoulder; nearly vertical umbilicfc.1 wall, fairly deep umbilicus.
Last whorl with six progressively prorsoradiate constrictions starting frou prominent slightly elongated umbilical tubercles, much projected over the venter, three or four ribs of varying lengths between each pair of constrictions; progressively prorsoradiate and much projected over venter, some of the ribs splitting at raidside tubercles.
Remarks ! The specimens agree with j^achydiscus anapadense
Kossinat in all essential details, Matsumoto (1955) in his paper ’The bltuberculate Pachydtsclds from Hokkaido and
Saghalien has placed this species under the genus
Pseudojacobites Spath; but the author does not agree with his vieAv, since Pseudojacobites (Treatise L 377) is characterised by umbilical, ventrolateral aid siphonal
Th 5 743 - 101 -
tubercles, while this species as Instituted by Kossmat Is
without siphonal tubercles and hence It should be placed
under Lewesiceras Spath.
Sastry, Rao and Mamgain (1968) in their paper
'Biostratigraphic Zonation of the Upper Cretaceous Formation
of Trichin*poly District, South India' have given a
photograph of Pseudojacobites anapadense PI, II (7r 8), It
has no siphonal tubercles, hence it should be included in
genus Leweaiceras and labelled as Lewesiceras anapadense.
Occurrence : Our specimens are collected from limestones
of Trichinopoly Group at Saradamangalam.
Lewesiceras va.ju (Stoliczka)
( PI. XXXIX, Figs. 1, 2 )
1865 Ammonites va.iu Stoliczka : Stoliczka, p. 132, pi. LXV, Fig. 3.
1968 Lewesiceras va.ju (Stoliczka) : Sastry, Rao & Mf*mgain, PI. 2, Figs. 9, 10.
Material : One specimen.
Pleslotype t MACS G 1371
Measurements : b/h = 0.99, u/d = 0.32
Description ! Shell rather evolute,with a whorl section nearly
circular; semicircular venter; maximum width in the mid-lateral
region; subrounded umbilical shoulder; steeply inclined umbilical wall; rather deep umbilicus. - 102 -
The available solitary fragment (l/2 whorl) shows four
progressively prorsoradiate constrictions projected over
venter; the inner bordering rib is prominent and starts
from umbilical tubercle. Between the constrictions arc two
to three ribs, progressively prorsoradiate^.projected over venter and of unequal lengths.
Remarks : The solitary specimen agrees in all essential respects with Ammonites va.iu Stollczka.
Occurrence : The specimen is collected from buff coloured
limestones of Trichlnopoly Group at Saradamangalam,
Genus ! Pseudo.lacobites Spath, 1922
Pseudo.jacobltes rotallnus (Stol.)
( PI. XL, Figs. 1, 2, 3; 1 ^ )
1865 Ammonites rotallnus Stollczka ; Stollczka, p. 65, PI. XXXIV, Fig. 2.
1897 Pachvdiscus rotallnus (Stollczka) ; Kossmat, p. 91, Taf. XIV,Fig. 2.
Materlal : One specimen.
Plesiotype : MACS G 1372 .
Measurements : b/h =1,3, u/d = 0,40 - 103 -
Description ; Evolute shell, whorl section depressed,
broader than high; broad semicircular venter; convex whorl
sides, broadest at a little distance from the umbilical
margin; subrounded umbilical shoulder; steeply inclined
umbilical wallj deep umbilicus.
This solitary fragmentary specimen has five to six
constxictions starting from strong, elongated umbilical
bullae, slightly prorsojadlate, projected over venter. Four
ribs between two constrictions become weaker towards umbilicus;
slphonal and mid-lateral tubercles and umbilical bullae.
Itemarks : Though fragmentary our speciiuan agrees in all
essential respects with Amu.onltes rotalinus Stoliczka.
According to the Treatise (L377), it should be classified on
the basis of tubercles under t^seudo.lacobites. Stoliczka's
specimen of Amnionites rotalinus is reported from Utaturs, but our specimen comes from Trichlnopoly Group, and hence its range should be extended into Turonlan,
Occnrrence : Thejfespecimen is collected from the buff coloured
limestones of Trichlnopoly Group at Saradamangalam.
Pseudo.lacobltes gharei sp. nov.
( PI. XLI, Figs. 1, 2, 3 )
Muterial ; One specimen. - 104 -
Holotype : MACS G 1373.
Measurements I b/h = 1.4, u/d = 0,30
Description : Involute shell, whorl section depressed, convex whorl sides, broadest In the mid-lateral region; subangular umbilical shoulder; steeply inclined umbilical wall.
Last whorl shows nine constrictions not much prorsoradiate nor projected over venter end carry three rows of tubercles - umbilical, ventrolateral and siphonal.
Between the constrictions are ribs which are faint and without any tubercle.
Remarks : By its much involute shell; constrictions with rounded unibilical tubercles and the ribs without tubercles, this species can be distinguished froDi Pseudo.1 acobites rotalinus (Stol.).
Occurrence : The^ specimen cones from limestones of
Trichinopoly Group at Sattanur.
Genus : Nowakites Spath, 1922
Nowakltes .1 imboi (Kossmat)
( PI. XLII, Figs. 5, 6 )
1865 Ami.ionites denisonianus Stoliczka : Stoliczka, pi. LXV, Fig. 4, 4a; non-fig.1, 2 of PI. LXVI. - 105 -
1897 Paohydiscus .limbo 1 Kossmat : Kossmat, p, 157, Taf. XIV (XX), Figs. 1 a, b,
1968 Nowakites .jimboi (Kossmat) ; Sastry, Rao & Masgailn, PI. Ill, Figs. 9, 10.
Material ; Two specimens.
Plesiotype : ilACS G 1474.
Measurements :
• J No. • b/h u/d • •
MACS G 1374 0.83 0.29 MACS G 1375 0.81 0.28
Description : Rather involute shell; whorl section compressed, with sides nearly flat; semi-circular venter; subroundcd
umbilical shoulder; steeply Inclined nearly vertical umbilical wall; umbilicus not very deep.
Last whorl with seven progressively prorsoradiate constrictions not much projected over the venter, the inner
bordering rib quite prominent and starting from an umbilical
tubercle.
Inter-constrictioc ribs four to seven, unequal in
length, sOEie reaching the umbilical border, oblique, nearly
parallel to the constrictions, but not much projected over the venter. - 106 -
Remarks : Both the specimens agree with Pachydlscus .llmboi described by Kossmat. For distinction from Nowakites saradamangalensis see under that species.
Occurrence ; The^specimens are collected from yellow to buff coloured limestones of Trichinopoly Group at Saradamangalam.
Distribution ; Besides South India this species is reported from Sontonian of Madagascar (Collignon, 1964).
Nowakites badvei sp, nov.
( PI. XLII, Figs. 1 to 4; Text Figs. 153 to 156 )
1864 Ammonites denisonianus Stoliczka Stoliczka, p. 133, PI. LXVI, non-fig. 2, PI. I.XVI, non-fig. 4, Pt. LXV.
Material : Two specimens.
Holotype ; MACS G 1376.
Measurements :
No. : b/h • u/d
MACS G 1376 0.83 0.31 MACS G 1377 0.82 0.31
Description : Rather evolute shell, with a compressed whorl section, slightly convex sides, with a semicircular venter and 156 - 107 - maximum width a little below the mid-flank region; sub- angular uc:billcal shoulder; nearly vertical umbilical wall; umbilicus not very deep.
The last whorl with eight progressively prorsoradlate narrow and shallow flexuous constrictions and much projected over the venter. The inner bordering rib quite prominent.
Three to five ribs between the constrictions; flexuous and much projectnd over venter; the middle rib longer and bolder than the others and nearly reaching the umbilical border; other ribs of unequal lengths.
Remarks : By its more evolute shell, and constrictions and flexuous ribs, projected over the venter, the species can be distinguished from Nowakites .1 imboi (Kossmat) with which it is associated.
Occurrence : Thesfspecimens come from the yellow to buff coloured limestones of Trichlnopoly group at Saradamangalam.
Genus : Anapachydiscus Yabe & Shimizu 1926
Anapachydlscus arrlyaloorensls (Stollczka)
( PI. XLIII, Figs. 1, 2, 3 ISCJSI^ISZ)
1865 Ammonites arrlaloorensls Stollczka ; Stollczka, p. 126, Pl.LXIIT, Figs. 2,3, - 108 -
1897 Pachydiscus arlyalurcnsIs (Stoliczka) ; Kossmat, p. 103, (No fIture).
1932 Parapachydiscus arlyalurensls (Stoliczka) : Colllgnon, PI. VI, Fig. 4.
1968 Anapachydlsciis arlyalurensls (Stoliczka) : Sastry, Rao,uv,£^ Maiqgaln,pl, IV, Figs. 7,8,
Material ; Two specimens (fragments about half whorl)
Pleslotype : MACS G 1378.
Measurements ;
No. • b/h • u/d
MACS G 1378 1,2 0,24 MACS G 1379 1,3 0,28
Description ; Rather Involute shell; whorl section depressed, whorl sides convex with abroad semicircular venter; maxiinum width in the midlater«l area; subrounded umbilical shoulder.
The available fragments show four to five constrictions
(8-10 for complete whorl) which ere broad and shallow, slightly prorsoradiate, not much projected over venter with the inner bordering rib starting from prominent fairly large umbilical bullae,
P-ibs, two to four between constrictions; not much prorsoradiate nor much projected over venter, becoming weal towards the umbilicus. 15 52 - 109 -
Remarks ; The specimens agrpe in all essential respects with y Amronites arri,aloorensis StolicKka. Colllgnon (1932) has described Parapachydlscus arlyaloorensis (Stol.) from
Campanian rocks of Madagascar, but according to the Treatise the characters of Ammonites arr^aloorensis Stoliczka fit into " " ' ' ' f Anapachydiacus (p. L 380) and not Parapadhydiscus (=Pachydiscus). and hence we place our material and also of Collignon under the genus Anapachydiscus.
Occurrence ; From gritty limestones of Ariyalur Group of
Mettal.
Distribution : i^esides South Indio, it is reported from the rocks of Campanian age of Madagascar by Collignon (1932).
Anapachydiscus sp. indet -
( PI. XLIV, Figs. 1,2 )
Material : One specimen (fragment).
Figured specimen N o . : MACS G 1380.
Measurements : b/h = 0.89 u/d = 0.32
Description : Fairlyevolute shell, with compressed whorl section, only a little higher than broad; whorl sides - 110 - slightly convex, venter broad semlclrcularf maxiraura width little above umbilical shoulder; umbilical shoulder sub rounded; steeply inclined umbilical wall; umbilicus rather deep.
a The solitary fragment (nearly halfj^whorl) shows four falcoid constrictions starting from umbilical elevation; they are progressively prorsoradiate much projected over venter. Between the constrictions are two to three ribs running parallel to constrictions; the ribs are of unequal lengths becoming obsolete near umbilical region.
Occurrence : From yellow to buff coloured limestones of
Trichinopoly Group at Saradamangalam. m 3 C K t I V •c tt) C5 >. (U 'D x: ■M T-t o •H O ca • «►