A new genus of Cretaceous margaritine gastropod (Turbinidae) from the northeastern Pacific Ocean

2011·9.5 MB·English

by  Richard L Squires

1
THE NAUTILUS 125(3):137-149, 201 Page 137
A new genus of Cretaceous margaritine gastropod (Turbinidae)
from the northeastern Pacific Ocean
Richard L. Squires
DepartmentofGeological Sciences
California State University
Northridge, CA91330-8266, USA
and
Invertebrate Paleontology1
Natural History Museum ofLos Angeles Count)'
Los Angeles, CA90007 USA
[email protected]
ABSTRACT assigned to other similar-looking genera. In addition
to erecting the new genus, the main pin-poses of this
Igonoia, a new genus ofa margaritine vetigastropod, is recog- paper are to describe its species and to record their
nizedfrom Lowerand UpperCretaceousrocksinthenortheast- biostratigraphic succession. The areas where the spec-
ern Pacific, in the region extending from Vancouver Island, imens were collected are shown on Figure 1, and their
British Columbia, to southern California. Eight species are
known, five are new: the early late Albian I kieli new species designations (e.g.. Area 3) are used throughout the
and 1. shastana new species; the late Cenomanian I onoensis paper. The details of the type localities of the species
new species and I stewarti (Murphy and Rodda, 1960) new are given in the Appendix. The temporal distributions
combination; the late Turonian /. vacca new species; the of the species are shown in Ligure 2. Paleogeographic
Santonian I. occidentalis (Whiteaves, 1903) new combination; and paleoclimatic conditions of the new genus are
and the Maastriehtian I. angulata (Gabb, 1869) new combina- discussed.
tion and I. muiri newspecies. Igonoia is presently known to be Included in this paper are supplementary descrip-
endemictothestudyarea. Specimens are found predominantly tions (based on new examination ot type material)
in northern California, in fine-grained siliciclastic sandstones and refined biostratigraphic records ofthe three previ-
thatwere deposited inwarm-temperate, shallow-marinewaters. ously named species: Igonoia angulata (Gabb, 1869);
Specimensare mostnumerous in Santonian rocks.
Igonoia occidentalis (Whiteaves, 1903); and I. steward
Additional keywords: Mollusea, Margaritinae, fossil, endemic, (Murphy and Rodda, 1960). New information about
temperatewaters the type locality of I. angulata is provided, and its
type material consists of two species: 1. angulata and
I. muiri new species. The first photographic views of
the type material of I. occidentalis are provided. Addi-
tional photographic views of I. steward are given, and
INTRODUCTION its type material consists oftwo species: I. steward and
I. ononensis new species.
Small trochiform vetigastropods present in Cretaceous This study was based on 260 specimens borrowed
shallow-marine rocks of the northeastern Pacific are from museums having extensive collections ofnortheast
poorly documented in the literature. In the authors on- Pacific Cretaceous fossils. Most of the specimens
going process of attempting to establish which genera are stored in the Invertebrate Paleontology Collection at
are present, a new genus of margaritine vetigastropod the Natural History Museum of Los Angeles County.
was detected in museum collections. The new genus The base and umbilical areas of the specimens are
Igonoia occurs in both Lower and Upper Cretaceous commonly encased in well-cemented, fine-grained
shallow-marine rocks in the region extending from Van- siliciclastic sandstone. In order to remove this material,
couver Island, British Columbia, Canada to southern it was necessary to use a high-speed drill and diamond-
California. Specimens are locally abundant but are coated grinding wheels, followed by the careful use
otherwise uncommon faunal elements. There are eight of hand-held, very sharp needles. Preservation of shell
known species of the new genus, and five of them are material is generally good. Protoconch and early
new. The three previously named ones were originally teleoconeh whorls are very rarely present, and mostly or
completely decollated. The one moderately well pre-
1 Research Associate servedprotoconch with its shellintactwas sputter-coated
,
Page 138 THE NAUTILUS, Vol. 125, No. 3
Ma
Maastr. 1 Jfe Igonoia Igonoia
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u 1 Igonoia
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Igonoia Igonoia
Cenom. onoensis stewartl
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Figure 2. Geologic ranges ofthe studied species ofIgonoia.
Ages ofstageboundaries from Gradstein et al. (2004).
Genus Igonoia new genus
Figure 1. Localities mapandlatitudinaldistributionofstudy Type Speeies: Igonoia onoensis new species, late
Cenomanian, northern California.
areaspecies ofIgonoia.
Description: Shell size veiy small to medium small
mm
(4.5 to 13 height). Shell height commonly slightly
prior to being imaged by means of an Hitachi S-3000N less or approximately same size as shell diameter, rarely
SEM greater than diameter. Trochiform. Phaneromphalous.
(scanningelectron microscope).
Abbreviations used for catalog and locality numbers Spire low to moderately high, 43% to 59% of shell
are: ANSP: Academy of Natural Sciences, Philadelphia; height. Pleural angle 80° to 95°. Protoconch smooth
GSC: Geological Survey of Canada, Ottawa; LACMIP: (mostlikelyless than onewhorl),transitiontoteleoconch
Natural History Museum of Los Angeles County, Inver- unclear. First teleoconch whorl showing spiral threads
tebrate Paleontology; UCLA: University of California, before showing any axial ribs. Teleoconch four to six
Los Angeles (collections now housed at LACMIP); convex whorls; base usually rounded. Suture sunken
USGS: United States Geological Survey, Menlo Park, and commonlygroove-like. Teleoconch ornament ofspi-
California (collections now housed at University of Cali- ral ribs (beaded or unbeaded), commonly crossed by
fornia, Berkeley, Museum ofPaleontology). raised growth lines, especially on ramp/shoulder areas;
shells can be nearly smooth. Shoulder rounded. Aper-
ture circular. Peristome discontinuous. Last whorl large,
SYSTEMATIC PALEONTOLOGY base convex or keeled. Umbilicus open and deep,
bounded by beaded weak to moderately strong spiral
Clade Vetigastropoda Salvini-Plawen, 1980 rib; umbilical wall can have cancellate ornament where
FamilyTurbinidae Rafinesque, 1815 growth lines intersect spiral ribs.
Subfamily Margaritinae Stoliczka, 1868
GeologicAge: EarlylateAlbianto“mid” Maastrichtian
(early late to late middle).
Remarks: This subfamily was previously generally
believed to be a trochid subfamily (e.g., Fretter and Etymology: Named for the adjacent towns ofIgo and
Graham, 1977; Hickman and McLean, 1990), but, based Ono in the Bald Hills area, Shasta County, northern
on molecular studies ol extant taxa by Williams et al. California.
(2008), it has been recentlyand provisionally recognized
tobe aturbinid. Williams et al. (2009) demonstrated that Remarks: Aftercarefulexaminationofeach specimen,
Margaritinae is not monophyletic. only two were found with remnants oftheir protoconch
R.L. Squires, 2011 Page 139
present. Only one of these, a specimen ol I. onoensis by having a discontinuous peristome, sunken suture,
(Figures 21-22), has the shell intact on its protoconch, shoulderwith raised growth lines with orwithout axially
whereas the other, aspecimen ofI. shastana (Figure 14), alignedbeads, whorl sideswith orwithoutaxiallyaligned
is missing its shell on the protoconch and adjacent early beads, and commonly an absence of a very prominent
teleoconchwhorls (onlyan internal mold is present). spiral rib borderingthe umbilicus.
Gabb (1869) originally assigned the material that Igonoia is similarto genus Margarites E. Gray, 1847
J.
is now known to comprise I. cingulata (Gabb, 1869) (ex Leach ms), but Igonoia differs by having a ramp or
and I. muiri new species to genus Margaritella Meek shoulderwith raised growth lines with orwithout axially
and Hayden, 1860, a nomen dubium (not Margaritella aligned beads, whorl sides with or without axially beads,
Thiele, 1891). and commonly a less prominent spiral rib bordering the
The other previously named species of Igonoia were umbilicus.
assigned eventually by other workers (Whiteaves, 1903;
Stewart, 1927; Murphy and Rodda, 1960) to the Igonoia kieli new species
(Figures 3-8)
solarielline genus Solariella Wood, 1842. This is not
surprising, given that Hickman and McLean (1990) Diagnosis: Small-sized Igonoia ramp slightly con-
reported that solariellines are known to have produced cave, moderately wide, and bearin,g up to three beaded
convergences with margaritine shells. Fossil species of spiral ribs (posteriormost ones more prominent); whorl
Solariella have been characterized (e.g., Davies, 1971; sides smooth or with some prominent growth lines pre-
Kiel and Bandel, 2001) as having a continuous peri- sent andextendingposteriorward across ramp.
stome, spiral cords that can be strongly noded, a keel on
thebase ofthe shell, andaveryprominent spiralcordon Description: Shell size small (up to height 8 mm,
the rim ofthe umbilicus. Igonoia differs from Solariella diameter 9 mm, same specimen). Shell height
Figures3-16. AlbianspeciesofIgonoianewgenus. Specimenscoatedwithammoniumchloride.3-8.Igonoiakieli newspecies.3-7.
Holotype LACMIP 13682, LACMIPloc. 22900, height 8.7 mm, diameter9.4 mm. 8. Paratype LACMIP 13683, LAGMIP loc. 22900,
height 6.6 mm, diameter 8.4 mm. 9-16. Igonoia shastana new species. 9, i1, 13, 14, 15. Holotype LACMIP 13684, LACMIP loc.
28757,height6.3mm, diameter6.2mm. 10, 12, 16. Paratype LACMIP 13685, LACMIPloc. 24369, height7.5mm, diameter8.1 mm.
Page 140 THE NAUTILUS, Vol. 125, No. 3
approximately 92% of shell diameter. Trochiform. The single specimen ofI. kieli from loc. 24369 is from
Phaneromphalous. Spire moderately elevated, approx- theVenado Sandstone. This memberis ofearlyTuranian
imately 54% ofshell height. Pleural angle approxiately age and contains reworked Albian fossils (Squires and
87°. Protoconch unknown. Teleoconch approximate- Saul, 2004).
ly five convex whorls. Suture impressed. Ramp slightly Igonoia kieli differs from I. shastana by slightlylarger
concave and moderatelywide. Upper spire whorls with size, subsutural rib, much less uniform ornament, and
two subsutural and equal-strength beaded spiral ribs; obsolete ornament on the sides of the whorls. Igonoia
penultimate whorl with three beaded spiral ribs, all kieli is similar to 7. muiri new species, but I. kieli differs
nearly equal strength. Ornament on last whorl with six by having larger size, subsutural rib much weaker on
spiral ribs, posteriormost two beaded (elongate beads) spire whorls, absence of flat ramp, less angulate shoul-
and equal strength, anteriormost four ribs unbeaded der, more spiral ribs on shoulder, and much less promi-
and weaker strength. Ornament on whorl sides obso- nentgrowth lines incisingthe spiral ribs onthe shoulder.
lete or with some widely spaced, prominent growth Igonoia shastana new species
lines present and extendingposteriorward across ramp.
(Ligures 9-16)
Base demarcated by low angulation. Ornament on base
consisting ofmanyclosely spaced unbeaded spiral ribs, Diagnosis: Small-sized Igonoia spiral ribs numerous
anteriorward becoming broader and beaded toward and uniformlynodedexcepton ant,eriorhalfoflastwhorl
umbilicus and producing cancellate ornament. Aper- and on posteriorpart ofbase oflastwhorl.
ture subcircular. Outer and inner lips thin. Peristome
discontinuous. Umbilicus wide, its rim angulate and Description: Shell size small (up to height 7 mm,
demarcated by moderately strong and beaded spiral diameter 8.5 mm, same specimen). Shell height
rib. Umbilical wall with stronger cancellate ornament approximately 92% of shell diameter. Trochiform.
than area immediately posterior to umbilical rim. Phaneromphalous. Spire moderatelyelevated, approxi-
Growth lines prosoeline, tilted 28° from vertical. mately 50% of shell height. Pleural angle approxi-
mately 84°. Protoconch most likely less than one
Holotype: LACMIP 13682, height 8.7 mm, diameter whorl. Teleoconch approximately 4.5 whorls. Suture
9.4 mm. impressed. All whorls with rounded sides. Ornament
obsolete on two earliest whorls. Ornament on
Paratype: LACMIP 13683, LACMIP loc. 22900. remaining whorls consisting of many closely spaced
Type Locality: LACMIP 22900, Bald Hills, Ono area, spiral ribs, beaded except on anterior halfoflastwhorl
and on posteriorpart ofbase oflastwhorl. Base demar-
Shasta County, northern California (Area 3).
cated by low angulation. Spiral ribs on base
GeologicAge: EarlylateAlbian (upperOxytropidoceras anteriorward becoming wider and bearing beads that
packardi ammonitezone). become elongate nearumbilical rim. Aperture circular.
Outer and inner lips thin. Peristome probably dis-
Distribution: Buclden Canyon Lormation, Chickabally continuous. Umbilicus wide, its rim angulate and
Mudstone Member, Bald Hills, vicinity of Ono, Shasta demarcated by spiral rib wider and more strongly
County, northern California (Area 3); reworked beaded than adjacent spiral ribs on base. Umbilical
Albian fossils in lower Turanian Venado Sandstone wall cancellate. Area abaxial to umbilical rim with
just south of Sites, Colusa County, northern California irregularly spaced incised growth lines. Growth lines
(Area5). prosoeline, tilted approximately35° from vertical.
Etymology: Named for Steffen Kiel who has made Holotype: LACMIP 13684, height 6.3 mm, diameter
significant contributions to the study of Cretaceous 6.2 mm.
vetigastropods. Paratype: LACMIP 13685, LACMIP loc. 24369.
Remarks: The examined material consisted of six Type Locality: LACMIP 28757, Thompson Canyon,
specimens: live from loc. 22900 (type locality) and one Yolo County, northern California (Area 6).
from loc. 24369. Preservation is generally good. Igonoia
kieli co-occurs with I. shastana new species at Iocs. GeologicAge: EarlylateAlbian(upperOxytropidoceras
22900 and 24369. Locality 22900 is from the upper part packardi ammonitezone).
of the Chickabally Mudstone Member, and Murphy
(1956: figs. 3-5) plotted this locality (as loc. 2900) on Distribution: Budden Canyon Formation, upper
his columnar section and on his geologic maps. On his Chickabally Mudstone Member, Bald Hills, Ono area,
figure 6, he plotted this locality near the top of the Shasta County, northern California (Area 3); reworked
Oxytropidoceras packardi ammonite zone, and on the Albian fossils in upper Cenomanian “Antelope” shale
biostratigraphic chart shown by Murphy et al. (1969: (upperpart),justsouthof Sites, ColusaCounty, northern
fig. 2), it appears that this part ofthe zone is early late California (Area 5); and reworked Albian fossils in
Albian in age. Turanian Venado Sandstone, Thompson Canyon, north
R.L. Squires, 2011 Page 141
of Putah Creek, Monticello Dam area, Yolo County, spiral threads; after another 180°, weaker spiral ribs dis-
northern California (Area6). appear but spiral threads (two) on or near shoulder con-
tinue and become incipiently beaded. All teleoconch
Etymology: Named for its occurrence in Shasta whorls with rounded sides. Suture impressed. Ramp
County, northernCalifornia. rounded, narrow, and covered by four to five equant
spiral ribs bearingprominent elongate beads arranged in
Remarks: The examined material consisted of eight rows. Ornament on whorl sides consistingofweak (rarely
specimens: three from USGS loc. M-177 (see Squires obsolete) unbeaded spiral ribs. Aperture subcircular.
and Saul [2004: 500] for locality details); two from Outer and inner lips thin. Peristome probably discontin-
LACMIP loc. 22900; two from 24369; and one from uous. Base ornamented with several strong, moderately
28757 (type locality). Distinction between the pro- narrow spiral ribs. Umbilicus wide, its rim angulate and
toconch and earliest teleoconch whorl cannot be made demarcated by nodulose wide spiral rib. Area abaxial to
because the shell is missing in these areas. umbilicalrimwidiirregularlyspacedincisedgrowthlines.
Igonoiashastana co-occurs with I. kieli new species at Growth lines prosocline, tilted 35° fromvertical.
locality22900 in the upperpart ofthe Chickabally Mud-
stone Member, and both co-occur as reworked Albian Holotype: LACMIP 13686, height 7.2 mm, diameter
material at loc. 24369 in the Venado Sandstone. The 7.2 mm.
USGS loc. M-177 specimens also represent reworked
material but are from the upper part of the “Antelope” Paratype: LACMIP 13687, LACMIP loc. 23476.
m
shale in beds approximately23to30 belowthe base of Type Locality: LACMIP 23476, Bald Hills, Shasta
the overlyingVenado Sandstone.
Accordingtothe LACMIP records, loc. 28757is in the County, northern California (Area 3).
Yolo Formation. On Matsumotos (I960: fig. 9) map, this Geologie Age: Late Cenomanian (slightly older than
locality plots near the contact between this formation Igonoia stewarti).
and the underlyingVenado Sandstone. Locality 28757 is
most likely located in the Venado Sandstone, thus the Distribution: Budden Canyon Formation, Bald Hills
specimens are also reworked material. Member, Bald Hills, Ono area, Shasta County, northern
Igonoia shastana and 7. kieli are somewhat similar in California (Area3).
that their earlywhorls are smooth and a portion oftheir
Etymology: Named for the town of Ono, Shasta
last whorl has either diminished or obsolete ornament.
County, California.
Igonoia shastana differs from 7. kieli by slightly smaller
size, absence of a subsutural rib, meh more uniform Remarks: Examined material consisted of four spec-
ornament, and ornament on the sides of the whorls. imens (one early? adult and three juveniles), all from
No known specimens show intermediate morphology LACMIP loc. 23476 in the middle part ofthe Bald Hills
between the two species. Future collecting might reveal Formation. One ofthejuveniles has itsprotoconch intact
such specimens, and, hence, the two species could be (Figures 21-22). Murphyand Rodda (1960) did not rec-
shown to be conspecific. ognize that the specimens they identified as S. stewarti
Igonoia onoensis new species from LACMIP loc. 23476 represent a different species
(Figures 17-23) than S. stewarti. Although both species occurin the Bald
Hills Member, S. onoensis is found slightly downseetion
Sollariellastewarti Murphyand Rodda, 1960: 839 (in part). from S. stewarti.
Murphy and Rodda (I960: fig. 2) reported that the
Diagnosis: Small-sized Igonoia ramp rounded and aporrhaid gastropod Arrhoges Latiala califomicus
, ( )
covered by four to five spiral ribs bearing prominent (Gabb, 1864) occurs at LACMIP loc. 23476. Popenoe
beads arranged in rows, whorl sides with weak and (1983) assigned this aporrhaid a Cenomanian? to early
unbeaded spiral ribs, and basal ornamentstrong, includ- Turanian age.
ingwide umbilical cord. The new species is similar to Igonoia stewarti but
7. onoensis is characterized by having prominently
Description: Shell size small (up to height 7 mm, beadedspiral ornament, whereas 7. stewarti is character-
diameter 7 mm, same specimen), glossy surface. Shell ized by having weaker ornament consisting of raised
heightapproximatelysame as shell diameter. Trochiform. growth lines. In addition. 7. onoensis differs by having
Phaneromphalous. Spire moderately elevated, approxi- smallersize, more slopedramp, beaded spiral ribs on the
mately56% ofshellheight. Pleuralangle92°. Protoconch ramp, nearly obsolete spiral ribs on sides of the whorls,
smooth (most likely less than one whorl), transition to and slightlystrongerornament on the base.
teleoconch unclear; first half whorl of shell measures The new species most resembles Igonoia main new
mm
0.38 (380 pm) diameter. Teleoconch approximately species but differs by having a larger size, no subsutural
five whorls. Earliest teleoconch whorl with two equal- cord, roundedshoulder(ratherthan angulate),andshoul-
strength spiral threads (one on shoulder and one just der demarcated by several equal-strength spiral ribs,
anterior to shoulder) and three to four much weaker rather than by only two spirals, with the posteriormost
Page 142 THE NAUTILUS, Vol. 125, No. 3
Figures 17-29. CenomanianspeciesofIgonoianewgenus. Specimenscoatedwithammoniumchloride. 17-23. Igonoiaonoensis
newspecies. 17, 18, 19,20,23. HolotypeLACMIP 13686,LACMIPloc.23476,height7.2mm,diameter7.2mm. 21-22. Paratype
LACMIP 13687, LACMIP loc. 23476, height 3 mm, diameter4.5 mm. 21. Abaperturalviewofspire tip. 22. SEM image ofleft-
lateral viewofprotoconch andearlyteleoconehwhorls,width ofview2.5mm. 24-29. Igonoiastewarti (Murphyand Rodda, 1960).
24,25, 27, 28, 29. Holotype LACMIP9821, LACMIPloc. 23763, height8 mm, diameter8.9mm. 26. Hypotype LACMIP 13688,
LACMIPloc. 23465,height6.2 mm,diameter6.9mm.
thestrongest. Inaddition,on I.onoensis,theornamenton Description: Shell size small (up to height 8 mm, di-
thebase is notas weakabaxially. ameter 9.2 mm, same specimen), glossy surface. Shell
height approximately 89% of shell diameter. Trochiform.
Igonoia stewarti (Murphy and Rodda, I960) new Phaneromphalous. Spire low, approximately 45% of
combination
shell height. Pleural angle 92°. Protoconch unknown.
(Figures 24-29) Teleoconeh approximately six whorls, all with rounded
Solariella stewarti Murphy and Rodda, 1960: 839 (in part), sides. Suture nearlyeanaliculated. Shoulderroundedwith
pi. 103, figs. 4-5. three to five spiral ribs (noded), commonly very weak
to weak. Spiral ornament elsewhere (on sides of whorls)
Diagnosis: Small-sized Igonoia with spire low, shoul- consistingof numerous and closelyspaced, weakto rarely
der rounded with numerous very line to fine spiral ribs moderately strong spiral riblets with tendency to being
crossed by prominently raised growth lines, basal orna- faint to obsolete. Shoulder with numerous and closely
mentweak, andumbilical cord moderatelystrong. spaced, weak to moderately strong ribs coincident with
R.L. Squires, 2011 Page 143
prominently raised growth lines. Aperture subcircular. dillen from loe. 23464. Rodda (1959) assigned this
Outer and inner lips thin. Peristome probably discontin- ammonite a Cenomanian age. Murphy and Rodda
uous. Base ornamented by numerous, very weak spiral (1960) also reported that S. stewarti is also present
riblets. Umbilicus rim angulate and demarcatedbysome- in the “formation” that overlies the Bald Hills “forma-
whatnodulose, moderatelystrongtostrongspiralrib. Area tion.'' Using the revised stratigraphy of Murphy et al.
justposteriortoumbilical rim withirregularlyspacedribs. (1969), this overlying“formation” is the Gas Point Mem-
Areajustabaxialtoumbilicalrimcancellateonsomespeci- ber (Cenomanian to Turanian) of the Budden Canyon
mens. Umbilical wall cancellate. Growth lines prosocline, Formation. The present author, however, was unable to
tilted35° fromvertical. confirm a Gas Point Memberoccurrence ofI. stewart.
Holotype: LACMIP 9821 [= UCLA 28622], height Igonoia vacca new species
8 mm, diameter 8.9 mm. (Figures 30-34)
Paratype: LACMIP 9822 (unfigured here) [= UCLA Diagnosis: Small-sized Igonoia with spire low and
28683], LACMIP loc. 23763. teleoconch bearing widely spaced, narrow spiral ribs
crossed bywidely spaced and raised growth lines, espe-
Type Locality: LACMIP 23763, Bald Hills, Shasta ciallyon rounded shoulder.
County, northern California (Area3).
Description: Shell size small (up to height 7 mm,
Geologic Age: Late Cenomanian (slightly younger diameter 8 mm, same specimen). Shell height slightly
than I. onoensis). less or approximately same size as shell diameter.
Distribution: Budden Canyon Formation, Bald Hills Troehiform. Phaneromphalous. Spire low, approxi-
Member, Bald Hills, Ono area, Shasta County, northern mately 46% of shell height. Pleural angle 85°.
Protoconch unknown. Teleoconch approximately six
California (Area3).
convex whorls. Suture impressed; sutural area flattish
Remarks: The examined material consisted of nine on penultimate whorl. Teleoconch approximately four
specimens: four from LACMIP loc. 23464, three from convex whorls. Shoulder area rounded. Ornament
LACMIP loc. 23465, and five from LACMIP loc. 23763. consisting of widely spaced, narrow spiral ribs; spire
Preservation is good. Two of the specimens from whorls with five riblets; spiral ribs on last whorl some-
LACMIP locality 23465 have stronger spiral ribs than what clustered together: two near suture, one on
normal for this species, and one of these specimens is shoulder, four to five on sides ofwhorls, and numerous
illustrated in Figure 26. These variants were not men- ones on base. Spiral ribs on base gradually become
tioned by Murphyand Rodda (1960). slightly stronger near umbilical rim where raised
Murphy and Rodda (1960: 839) believed that growth lines cross spiral ornament. Aperture circular.
S. stewarti is represented by some ofthe type material Outer and inner lips thin. Peristome discontinuous.
of Igonoia angulata. During this present investigation, Umbilicus moderately wide, its rim angulate and
this latter material was studied and found to consist demarcated by beaded spiral cord with beads grading
of two species: I. angulata (Gabb) and I muiri new into nodes toward anterior end of columella. Umbilical
species. The latter species does resemble I. stewarti wall cancellate. Growth lines prosocline, tilted 30°
(see I. muiri for a comparison). from vertical.
Murphy and Rodda (I960) did not recognize that the
Holotype: LACMIP 13689, height 5.6 mm, diameter
specimens they identified as Soladella stewarti from
LACMIP loc. 23476 represent a different species. In 6.6 mm.
this present report, these specimens are identified as Type Locality: LACMIP 25421, east of Redding,
Igonoia onoensis new species, which is found in the ShastaCounty, northern California (Area 2).
middle part of the Bald Hills Member of the Budden
Canyon Formation. GeologicAge: Late Turanian.
Igonoia stewarti is present in the upper half of the
Bald Hills Member of the Budden Canyon Formation Distribution: Redding Formation, Melton Sandstone
a(tMeudrpmhaycraonfadunRao,ddaes,pe1c9i6a0l:ly83t9h,etsexpte-cfiieg.s 2o).f Tthhee gaassstorcoi-- iMfeomrnbiear(,Areeaast2)o;fLReaddddinFgo,rmSahtaisotna,CBoaunkteyr,CnaonrytohenrnMeCaml--
pods Gyrodes greeni Murphy and Rodda, I960 and ber, Santa Ana Mountains, Orange County, southern
Gijrodes allisoni Murphy and Rodda, 1960, are indica- California (Area 8).
tive of a late Cenomanian age (Popenoe et al., 1987: Etymology: Named for its occurrence in the Cow
fig. 1). Murphy and Rodda (1960: fig. 2) also reported Creek area east of Redding, Shasta County, northern
that the ammonite Desmoceras (Pseudouhligella) cf. California; vacca Latin, meaning cow, used as a noun in
barri/ae was found with S. stewarti at LACMIP loc. apposition. ,
23464, and Matsumoto (1959: 7) reported that tins
ammonite “seems to occur in the Cenomanian.” Mur- Remarks: Tlle examined material consisted of 17
phy and Rodda (1960) reported the ammonite Turnlites specimens, and nearly all of them are from the Redding
Page 144 THE NAUTILUS, Vol. 125, No. 3
Figures 30—41. Late Turanian and late Santonian species ofIgonoia new genus. Specimens coated with ammonium chloride.
30-34. LateTuranian Igonoia vacca newspecies, holotype LACMIP 13689, LACMIPloc. 25421, height5.6 mm, diameter5.6 mm.
35-42. Late SantonianIgonoiaoccidentalis (Whiteaves, 1903).Allspecimenscoatedwithammoniumchloride. 35,36,40. Hypotype
LACMIP 13690, LACMIP loc. 24217, height 8.7 mm, diameter 7 mm. 37-38. Paratype GSC 5918a, Nanaimo area, Vancouver
Island, British Columbia, height 5.5 mm, diameter 7.1 mm. 38. Left-lateral view. 39. Hypotype LACMIP 13691, LACMIP loc.
10794, height 7 mm, diameter 6.6 mm. 41. Hypotype LACMIP 13692, LACMIP loc. 24217, diameter 10 mm. 42. Paratype GSC
5919, Nanaimoarea,Vancouver Island, BritishColumbia, diameter6.9 mm,x5.4.
Formation. Most ofthe specimens have good preserva- Description: Shell size moderatelysmall (up toheight
tion. The new species somewhat resembles Igonoia 13 mm (estimated), diameter 12 mm, same specimen).
shastana new species, but the former differs by having Shell height approximately 15% greaterthan shell diam-
non-beaded spiral ribs and narrower and much more eter. Troehiform. Phaneromphalous. Spire moderately
widely spaced ribs. high, approximately 59% of shell height. Pleural angle
approximately 81°. Protoconch unknown. Teleoconch
Igonoia occidentalis (Whiteaves, 190.3) new approximately five to six whorls, all with rounded sides.
combination Suture impressed, rimed by prominent, unnoded
(Figures 35-42) subsutural cord. Shoulder narrow. Ornament generally
weak and crossed by raised growth lines. Upper spire
Solariella (radiatula ? var.) occidentalis Whiteaves, 1903: whorls with c-ancellate ornament. Lower spire whorls
3So6l8a-r3ie6l9l,aprio.d4d5a,ifiSgasu.l,5,159a5.9. with many wide-spaced, flat ribs separated by finely
incised lines. Last whorl similar to lower spire whorls,
except forbasewith manyweakandcloselyspacedspiral
Diagnosis: Moderately small-sized Igonoia with shell ribs that become slightly stronger anteriorward. Aper-
height greater than shell diameter, commonly with ture circular. Outer lip thin, inner lip thicker and
prominent subsutural cord, and raised growth lines projecting slightlyout over umbilicus. Peristome discon-
stronger than nearly obsolete spiral ribs, except on base, tinuous. Umbilicus moderately wide, its rim angulate
on subsutural spiral cord, and on umbilical rim. and demarcated by spiral rib, weakly beaded with beads
. .
R.L. Squires, 2011 Page 145
decreasing in strength anteriorward. Base oi last whorl Igonoia angulata (Gabb, 1869) newcombination
nearumbilical rim and umbilicalwall cancellate. Growth (Figures 43-47)
lines prosochne, tilted 30° from vertical. Margaritellaangulata Gabb, 1869: 172 [inpart],pi. 28,figs. 55.
Holotype: GSC 5918, height 4.7 mm, diameter Solariella angulata (Gabb). Stewart, 1927: 317, pi. 24, fig. 17.
6.9 mm.
Diagnosis: Very small-sized Igonoia with suture
Paratypes: GSC 5918a, 5918b, 5919, 5919a, all from canaliculate, ornament prominent only on shoulder,
the type locality. prominently raised growth lines on periphery and on
base oflastwhorl.
Type Locality: Vicinity of Nanaimo, Vancouver
Island, British Columbia (Area 1). Description: Shell size very small (up to height
4.5 mm (estimated), diameter 4.8 mm, same specimen).
GeologicAge: Santonian. Shell height approximately same as shell diameter.
Distribution: LOWER SANTONIAN: Haslam For- Trochiform. Phaneromphalous. Spire moderately high,
mation, Benson Creek and Nanaimo River, both in the approximately 54% of shell height. Pleural angle 80°.
vicinityofNanaimo, Vancouver Island, British Columbia Protoconch unknown. Teleoconch approximately four
C(rAereeka,1)e;asRteodfdRiendgdiFnogr,maSthiaosnt,auCpoupnetry,MenomrbteherrnV,CCalliofvoerr- wsihdoersl.s.ShoSuultdureer acuagnuallaitceu,lactreo.ssAeldl bwyhomralnsywpirtohmifnleantttilsyh
nia (Area 2). UPPER SANTONIAN: Redding Forma- raised growth lines that become obsolete near middle
tion, Member VI, Clover Creek, east ofRedding, Shasta portion of whorls. Spiral ornament obsolete on spire
County, northern California (Area 2); tentative occur- whorls; spiral ornament on last whorl consisting of
rence in Chico Formation, top of Musty Buck Member, many very fine threads starting at middle portion of
ChicoCreek, Butte County,northernCalifornia(Area4). whorls and continuing onto base. Base demarcated by
rounded angulation; base covered by many veiy fine
Remarks: Examined material consisted of 212 spec- spiral threads that become microscopically beaded
imens, which represents justs over 80% of the known anteriorward. Aperture elliptical. Outer and inner lips
studied specimensofIgonoia Preservation is moderately thin. Peristome probably discontinuous. Umbilicus rim
good. Whiteaves (1903) reported that some of his type angulate and demarcated by beaded spiral ribs.
material was collected (by others) from Brennan Creek Growth lines prosocline, tilted approximately 33° from
in the vicinity ofNanaimo, Vancouver Island. According vertical
to R. Graham (person, commun.), it should read Benson
Creek. Igonoia occidentalis is most abundant in lower Lectotype: ANSP 4238 (designated by Stewart (1927)
Santonian rocks at LACMIP loc. 24246 (Area 2), where but missing since 1992 (P. Colloman, person, commun.),
168 specimens have been collected. A few weathered height4.4 mm, diameter5 mm.
specimens tentatively identified as this new species are
from the top of the Musty Buck Member in the Chico Paralectotypes: ANSP 79512 [ex-ANSP 4238],
Formation, Butte County, northern California. Type Locality: LACMIP 23312, Franklin County,
Igonoia occidentalis is similar to Igonoia angulata but near Martinez, Contra Costa County, northern Califor-
differs from the latter by much larger shell size, suture
not canaliculate, presence of subsutural rib, and raised nia (Area 7).
growth lines extending from suture to suture on spire GeologicAge: “Mid” Maastrichtian (late earlyto mid-
whorls and from suture to umbilical rim on last whorl. dle late).
Igonoia occidentalis resembles the Upper Cretaceous
margaritineAtiraomatissima (Gabb, 1864) from Califor- Distribution: Panoehe Formation, Franklin Canyon,
nia but differs from the latter by having shell height southwest side of Martinez, Contra CostaCounty, north-
greaterthan shell diameter, subsutural cord, non-sloping ern California (Area 7).
ramp, more prominent growth lines, inner lip not
projected over edge of umbilicus, and umbilical rim Remarks: The examined material consisted of two
demarcated by au angulation rather than a prominent specimens, both previously part of a supposed group of
spiral rib. six ANSP paralectotypes of Solariella angulata. Five of
Stoliczka (1867-1868) reported Solariella radiatula these specimens are stored together as ANSP 79512 [ex
Forbes, 1846, from southern India at the locale of 4238] and the sixth one is ANSP 79153. Of the five
Odiyanr [= Odium of old usage], which, according to ANSP 79512 specimens, only two are like the drawing
Sundaram et al. (2001), is stratigraphically situated in provided by Gabb (1869) and the photograph provided
the upper Albian to Cenomanian Kami Formation. by Stewart (1927) ofthe lectotype ofS. angulata. Ofthe
Although Whiteaves (1903) questionably identified remainingthree specimens, two belongto Igonoia muiri
I. occidentalis as Solariella (radiatula ?var.) occidentalis, new species, and one is an indeterminate species
this species is here identified as I. occidentalis because it because it has lost most of its shell. The ANSP 79153
is not Forbes’s species radiatula. specimen is a badly crushed naticid? gastropod, and the
.
Page 146 THE NAUTILUS, Vol. 125, No. 3
Figures 43-51. Maastrichtian species ofIgonoia new genus. 43—47. Igonoia angulata (Gabb, 1869), paralectoype ANSP 79512
[e.v4238], LACMIPloe. 23312, height4.4 mm, diameter5 mm. 48-51. Igonoiamuiri newspecies, holotypeANSP81350, LACMIP
loc. 23312, height5.2mm, diameter7mm.
rock matrix filling its aperture is light in color, soft, and at Martinez, California. He assigned these strata to the
totally unlike the blackish-gray, well-cemented siltstone “Aturian,”which accordingto Haiiandet al. (1982: 1 10),
in the apertures ofthe two specimens of1. angulata and generallyrefers to the Campanian.
theGtawbobsp(1e8c6i9m)enrsepoofrIt.emduirthia.t the type locality ol his Igonoia muiri new species
S. angulata to be “at Martinez.” He (lid not collect the (Figures 48-51)
type specimens; theywere senttohim byacollector. The Margantella angulata Gabb, 1869: 172 [in part].
area immediately surrounding this city has stratigraphic Solaiiella angulata (Gabb). Stewart, 1927: 317 [inpart].
units ranging in age from Late Cretaceous to Miocene,
and there are several faults (Weaver, 1953). The location Diagnosis: Veiy small-sized Igonoia with spire low,
of the type locality of I. angulata, therefore, has been beaded subsutural rib, ramp flat, shoulder angulate and
poorlyknown; subsequently, the geologic age ofthis spe- bearing two spiral ribs (beaded), subsutural area and
cies has been uncertain. Inspection (by the present ramp incised by prominently raised growth lines, and
author) of the rock type associated with the two spec- sides ofwhorls smooth
imens of1. angulata revealed a match with the rocktype mm
associated with the gastropod Atira inornata (Gabb, Description: Shell size veiy small (up to height 5
1864), which is also found at LACMIP loc. 23312. (estimated), diameter 7 mm, same specimen). Shell
Squires (2010) reported that A. inornata is of “mid” height approximately90% ofshell diameter. Trochiform.
Maastrichtian age. According to the LACMIP records, Phaneromphalous. Spirelow, approximately43% ofshell
this locality is the same as Gabb's original “at Martinez” height. Pleural angle approximately 95°. Protoconch
Cretaceous locality. On Dibblees (1980) geologic map of unknown. Teleoconch approximatelyfourwhorls. Suture
tiie area, this locality plots in the Panoche Formation. impressed, bordered by prominent subsubtural beaded
Cossmann (1918: 257) based the earliest record ol rib. Ramp flat. Spire whorls with sides somewhat
genus Periaulax Cossmann, 1888, on “Margantella” rounded; last whorl with sides flattish. Ornament on
angulata Gabb, 1869 from the so-called “Chico Group” whorls consisting of beaded subsutural rib, stronger