sign in sign up
<<
Home , Anacoracidae, Anomotodon, Archaeolamna, Cretalamna, Hanna Formation, Ischyrhiza

Cainozoic Research, 8(1-2), pp. 13-28, December2011

Chondrichthyans from the Clayton Limestone Unit of the

Midway Group (: ) of

Hot Spring County, , USA

¹, ² Martin+A. Becker Lauren+C. Smith¹ & John+A. Chamberlain+Jr.

1 Department ofEnvironmentalScience, William Paterson University, Wayne, New Jersey 07470;

e-mail: [email protected]

2 Department ofGeology, Brooklyn College andDoctoralProgram in Earth and EnvironmentalSciences, City University

ofNew YorkGraduate Center, New York 10016; email:[email protected]

Received 7 September 2010; revised version accepted 26 June 2011

LimestoneUnit of The Clayton the Midway Group (Paleocene) in southwestern Arkansas preserves one ofthe oldest chondrichthyan

Cenozoic from the Gulf Coastal Plainofthe United assemblages yet reported States. Present are at least eight taxa, including; Odontaspis winkleriLeriche, Carcharias cf. whitei Carcharias 1905; (Arambourg, 1952); sp.; novus (Winkler, 1874); Cretalamnasp.;

obliquus Agassiz, 1843; Hypolophodon sylvestris (White, 1931); Myliobatis dixoni Agassiz, 1843; and a chimaeridofindeterminate

affiliation.Also present are lamnoid- and carcharhinoid-type chondrichthyan vertebral centra. The Clayton chondrichthyan assem-

blage derives from an outcrop locatedonly a few kilometersfrom a site exposing an assemblage ofMaastrichtianchondrichthyans from

Because and the upper Arkadelphia Marl. these assemblages are closely spaced stratigraphically geographically, they provide data on

chondrichthyan taxonomic turnover across the /Paleoceneboundary in this regionof the GulfCoastal Plain. The evolutionary

bottleneck in chondrichthyan diversity associatedwiththe end-Cretaceousmass event that hasbeendocumented fromother parts

ofthe world also appears to be strongly expressed inthe Arkansas region ofthe GulfCoastal Plain.

KEY WORDS:: Clayton LimestoneUnit,southwest Arkansas, chondrichthyans, Paleocene,K/P boundary.

Introduction formes (Kent, 1994; 1999a).

To date, only a few reports offossil chondrichthyans have

For over one and a quarter centuries, the occurrence of been documentedfrom Arkansas, none ofwhich occur in

Cenozoic chondrichthyan has been well- consecutive formations.These reports include: 1)two Mis-

documentedin North America. Earliest reports are those sissippian teeth from the Pitkin Formation and a single

offamous vertebrate such Edward paleontologists as Cope, Paleocene from the Midway Group (Freeman,

Othniel Marsh and who Joseph Leidy published numerous 1966); 2) sixteen from the uppermost San-

and identifications of Cenozoic chondrich- tonian-lowermost descriptions , including one new

from the Atlantic Coastal Plain Marsh, and from the thyans (ie.g. 1869; two new species Brownstown Marl (Meyer,

Cope, 1875a; Leidy, 1877). To date, most states inundated 1974); and, 3) at least seventeen species from the

by sea levelrise during the Cenozoic contain some record Arkadelphia Formation (Becker et al,

ofchondrichthyan fossils (e.g. Fowler, 1911; Thurmond 2006). This is surprising considering that the stratigraphic

& Jones, 1981;Wroblewski, 2004); and in some instances record in the southwesternpartofthe state consists largely

their in formations occurrence consecutive (e.g. Ward & of marginal and shallow marine limestone, sand, marland

Weist, 1990). Such occurrences in consecutive forma- chalk. It is also interesting to note thatthe shoreline ofthe

tions have provided an important basis for classifying the western GulfCoastal Plain ran through this region during

appearance of new species as well as documenting faunal much of the and early Cenozoic (Ken-

turnover and extinction of other species. This is particularly nedy etal., 1998). This shorelinereconstruction indicates

evident throughout the Chesapeake Bay Region where that entrance to the Western Interior Seaway from the

subtle changes in tooth morphology are stratigraphically east would have taken place across southwestern Arkansas

chronicled in major chondrichthyan orders such as Lamni- and nearthe base the Ouachita Mountains. -14-

Figure 1.

1. Hot Figure Location maps ofClayton LimestoneUnit(Paleocene) ofthe MidwayGroup andArkadelphia Formation(Maastrichtian),

Spring County, Arkansas. 1- late Maastrichtian - early Paleocene paleogeographicreconstruction oftheAtlantic and GulfCoastal

plainsand Western InteriorSeaway (redrawnfrom Kennedy eta!., 1998; Smith eta/., 1994). Dots indicatethe location ofPaleocene

chondrichthyansites discussed in thisstudy: A,New Jersey, (Fowler, 1911; Case, 1996); B, ChesapeakeBay Region, (Ward & Weist,

1990;Kent, 1994); C, SouthCarolina, (Purdy, 1998); D, , (Case, 1994); E, Arkansas, (Becker etal, 2006; this study); F,

Texas, (Stidham & Janus, 2008); G-H, South and North Dakota, (Cvancara & Hoganson, 1993); I, Wyoming, (Wroblewski,

2004); J, Montana, (Bryant, 1989). 2- Geologic map of Midway and Wilcox Groups (Paleogene) in the southwestern Arkansas

study area (modified from Haley etal., 1993). Location ofClayton LimestoneUnit chondrichthyan site (this study) indicated by

of Becker al. indicated 3- Detailed locator of Limestone Unit (X) and ArkadelphiaFormationsite et (2006) by (Y). map Clayton (X)

and ArkadelphiaFormation (Y) chondrichthyan sites discussed in this study. -15-

Figure 2. site. 1- Main collection Arrows indicate of white to chondrichthyan area. position light gray, highly fossiliferous

limestonebeds andthin beds oflight gray marl and sandy marl ofthe Clayton LimestoneUnit. The is disconform- able with the ofthe upper contact Clayton Limestone Unit and consists of light brown sands and limonite-stainedquartz gravel. 2—

Closeup ofCretalamnasp. tootheroding directly out ofClayton LimestoneUnit. 3-Closeup ofCarcharias cf. whitei (Arambourg, 1952)tooth eroding directly out of Clayton Limestone Unit. -16-

1 2

Arkansas. 1-White Figure 3.Closeup ofthe Clayton Limestone Unit ofthe Midway Group, Hot Spring County, to light gray, highlyfossilifer-

2- V in ous limestone bed with multiplesteinkerns of gastropodsand oyster shells; alve oftypical large oyster seen light gray marl and

sandy marl.

shoreline disconformities Such broad distribution of contemporaneous dense vegetative overgrowth. Regional

marine and shallow seaway across the Atlantic and GulfCoastal separate the Midway Group from the underlying

Formation and Plains as well as the Western InteriorSeaway may account Arkadelphia (Maastrichtian) overlying

similarities and in for the overall in genera species seen non-marineWilcox Group () (Haley etal., 1993).

which is North America chondrichthyan assemblages. Historically, the Midway Group over 180 metres

has not been dividedinto distinct geologic units. However,

Commission have In this paper, we describe a new chondrichthyan assem- recent studies by the Arkansas Geologic

blage recovered from the Paleocene Clayton Limestone identifiedexpansive clays withinthe Midway Group to be

Unitof the in Arkan- of construction Midway Group Hot Spring County, an area concern to practices (McFarland,

resulted in localized divisionof sas (Fig. 1). Although no new generaor species arereported 1998). Such concerns have

faunais be- into the Limestone Unit that here, the Paleocene chondrichthyan significant the Midway Group Clayton re-

cause it occurs stratigraphically directly above, and withina sides directly belowthePorters CreekClay Unit(McFarland,

few of of The LimestoneUnit consists of kilometers, an outcrop exposing an assemblage 1998). Clayton primarily

Maastrichtian from the limestone chondrichthyans upperArkadelphia highly fossiliferous, light-colored separated by

Marl(Becker etal., 2006). The Arkadelphia and Clayton thin beds of clay and sandy intervals while the Porters

Limestone assemblages provide a unique opportunity to Creek Clay Unit consists of highly expansive, dark-colored

study chondrichthyan taxonomic turnover across the Creta- calcareous clay with minimalfossil evidence.

ceous/Paleogene boundary and within close geographic Our Clayton LimestoneUnit site is approximately 3 kilometers

of proximity. Large scale, global studies ofKriwet & Ben- northwest ofMalvernand outcrops along both sides an

commercial ton (2004) have previously demonstratedthe devastating access road to a shopping facility (Figs. 1-

consist of white to effects of the K/P mass extinction event on these highly 2). Outcrop exposures light gray,

fossiliferous limestone beds to 0.5 meters thick mobile marinepredators. highly up that contain multiple steinkerns ofmollusks, particularly

gastropods and oyster shells (Fig. 3). Interbeddedwith the

Materials & Methods limestone are thin beds of light gray marl and sandy marl

typically less than 10 centimeterswithoccasional disarticu-

less Regional Geology, Location and Age lated oyster shells. Smallinvertebrate fossils, typically abundant the site and The Midway Group is a fossiliferous marginal marine deposit than2 centimeters, are throughout

Gulf include and skeletal structures ofmollusks, of Paleocene age that can be found throughout the shells, spines

Coastal Plain and several states ofthe Mississippi Embay- brachiopods, arthropods, echinoids, bryozoans and corals.

ment. In Arkansas, the Midway Group occurs in the Teethand vertebralcentra from chondrichthyans up to 3.5

centimeters also abundant and efforts southwestern part of the state along a northeastern trend are our collecting

that runs from Texarkana to Little Rock. Intermittent out- recovered a few teeth belonging to indeterminatespe-

the banks creeks cies of and brown sands and crop exposures occur along of and rivers pycnodonts gharials. Light

throughout this region where erosion has removed the limonite-stained quartz gravel of the Wilcox Group are -17-

disconformable with the contact of the 1905 1-12. upper Clayton Odontaspis winkleri Leriche, p. 117, pi. 6, figs.

LimestoneUnitand form erosion resistant buffs (Fig. 2).

The lower contact is obscured dense Materialexamined — ANSP by vegetation over- 23243, one anteriortooth; and alluvium growth Quaternary andterrace deposits near ANSP 23244, one lateral tooth. the banks of the Ouachita River and its tributaries. No

dark calcareous — colored, highly expansive, clay with Description Two teeth from 7-11 mm in total height; minimal fossil evidence ofthe central typical Porters Creek Clay cusp erect and slender in anterior tooth; distally

Unit ofthe Midway were identified at this curved and broader Group site. near the central cusp base in lateral

lines ofevidence of Multiple including magnetostratigra- tooth; pair narrow cusplets on mesial and distal root phy, ostracods, ammonites, chondrichthyans and osteich- lobes progressively smaller toward edge ofroot lobe; lin- thyans have been utilizedto establish a late Maastrichtian face age gual moderately convex and labialface relatively flat; forthe Arkadelphia Formation and Paleocene age for the both the central cusp and cusplets with multiple longitudi-

nal in anterior tooth overlying Midway Group (Cushman, 1949; Jones, 1962; ridges on lingual face; labial face

Liddicoat et al., 1981; Haley et al., 1993; Pitakpaivan & smooth in anteriortooth; lingual face in lateral tooth with

Hazel, Becker short 1994; et al., 2006; 2010b). Additionalde- longitudinal ridges near crown foot; lingual face scription oftheArkadelphia Formationand Midway Group smooth in lateral tooth; root lobes elongated and slender

well their with rounded biostratigraphy as as lithology are given in tips; holaucorhizous root with well-defined

Becker et al., nutritive (2006; 2010b). groove.

Discussion - Odontaspis winkleri teeth can be distin-

guished fromother teeth in the LimestoneUnit Field and Laboratory Techniques Clayton by

their smaller total height, narrow central of The Clayton LimestoneUnit chondrichthyan assemblage cusp, pair pro- smaller themesial is of gressively cusplets on anddistal root comprised approximately 2000 totalteeth and verte- lobes, and of brae recovered presence longitudinal on tooth crowns. Cur- across three seasons of fieldwork. In the ridges

there are at least fossils were rently, seven species of Odontaspis that field, collected through both sieving and sur- have been identified from the of face-collecting. Most productive collecting occurred after Cretaceous-Paleogene North America (e.g. Eastman, 1901; Leriche, 1905; rainfall events and during the colder months which re- Cap-

& Case, 1975;Case, 1981, Case & duced seasonal plant cover. The in situ specimens in the petta Borodin, 2000). Some of these taxa matrix ofthe fossiliferous limestonebeds are based on a few individual teeth were removed by from locations single and detailedstudy synonymize a pry bars, sledge hammers and chisels. Mesh sizes for siev- may number ofthese in the field from 1.0 species. ing ranged to 5.0 mm. Approxi-

Two of the more established taxa are O. aculeatus mately 250 kg of sediment was recovered for laboratory (Cap- sieve In the sediment petta & Case, 1975)from theCampanian-Maastrichtian and analysis. lab, was thoroughly washed

finer O. winkleriLeriche, 1905from the Paleocene-Eocene through progressively meshed screens ranging from (e.g. Ward 0.5 5.0 and dried & Wiest, 1990;Hoganson & Murphy, 2002; Becker to mm underheat lamps. Teeth were re- et ai, moved and 2006). Kent (1994) indicatedthat these two using amagnifying glass imaged directlywith an species can be distinguished by the larger overall size ofO. winkleri Olympus SZ61 BinocularMicroscope attached to an In- and the fact that this finity—2 Camera. species has reduced secondary cusplets Digital Because no new genera or spe- that less and cies identified the are divergent more erect. It is also important to were among specimens we recovered,

note that earlier abbreviated many taxonomic assignments presently as- synonymies are utilized. Specimens de- sociated with the Carcharias scribed here have been deposited in the fossil collec- genus wereoriginally placed with Odontaspis {eg. & Thurmond tions ofthe Academy of Natural Sciences Philadelphia, Cappetta Case, 1975; & Jones In Pennsylvania (ANSP). 1981). general, distinctions between the two

contemporaneous genera assigned from fossil teeth are

based the smaller tooth primarily on size and multiple, nar-

row cusplets that occur on both root lobes of Odontaspis. Systematic Paleontology

Genus Carcharias Rafinesque, 1810 Class Huxley, 1880

Subclass ElasmobranchiiBonaparte, 1838

Cohort Euselachii Hay, 1902 Carcharias cf. whitei (Arambourg, 1952) Order Berg, 1958 Figure 4.3a-4b Family Odontaspididae Muller& Henle, 1838

Genus Odontaspis 1838 Agassiz, 1931 teretidens Odontaspis White,p. 53,figs. 16-27; p. 54,

57. figs. 32-44; p.

winkleri 1905 Odontaspis Leriche, Materialexamined— ANSP 23245, one anterior tooth; Figure 4.1a-2b ANSP 23246, one lateral tooth. -18-

Figure 4.

Figure 4. Teeth of Odontaspididae, Cretoxyrhinidae, and from the Clayton Limestone Unit, Hot Spring

County, Arkansas. 1-2- Odontaspis winkleri (AN5P23243-23244);3-4- Carcharias cf. whitei(ANSP 23245-23246);5-6-

23249-23250); 10- Matrix of Carcharias sp. (ANSP 23247-23248);7-9- Cretalamnasp. (ANSP specimen ap- Orien- pendiculata (AMNH FF 20357); 11— Anomotodonnovus(ANSP 23252); 12-13-Otodus obliquus (ANSP 23253-23254).

tations: la, 2a, 3a, 4a, 5a, 6a, 7a, 8a, 9a, 10a, 11a, 12a, 13a= lingual view; lb, 2b, 3b. 4b, 5b, 6b, 7b, 8b, 9b, 11b, 12b. 13b =labial

view. Scale bars: 1-2, 4, 7—9 = 0.5 cm; 3, 5, 6, 10 = 1.0 cm; 12-13 =2.0 cm. 1-9, 11-13 = Clayton Limestone Unit.

10 = ArkadelphiaFormation. -19-

Description — Two teeth from 13-23 mm in total compressed in lateraltooth; well-definedcutting edges along height; central erect, slender and with the central with cusp sigmoidal cusp single, short, triangular and recurved

distal curve near in anterior face slight apex tooth; lingual cusplet on mesial and distal root lobes attached to central

moderately convex and labial face flat in anterior in relatively cusp labial view; weak lingual root protuberance on

tooth; central more triangular, broad-based and labio- anteriortooth with cusp one root lobeincomplete and one root lingually in lateral compressed tooth; single, triangular lobeelongated with roundedtip and poorly defined den-

mesial and distal root lobes attached cusplet on to central tal band in lingual view; root spatulate in lateral tooth

as seen in labial cusp view; multiple longitudinal ridges above a well-defined dental band; holaucorhizous root with the central base near directly aboveawell-definedden- well-definednutritive cusp groove. tal band face on lingual (see arrows in Figs. 4.5,4.7); well-

defined root lingual protuberance on anterior tooth; root Discussion The most frequently encounteredteeth in lobes rounded in anterior tooth, spatulate in lateral tooth; the Clayton LimestoneUnit belong to C. cf. whiteiandthis holaucorhizous root with well-defined, nutritive Carcharias groove. sp. Overall toothmorphology in boththese Clay-

ton LimestoneUnit species is very similar and taxonomic

Discussion - Carcharias cf. whitei teeth be distin- distinctions based the can are on presence or absence of guished from other teeth in the Limestone Unit Clayton by multiple longitudinal ridges onthe lingual crown face. Car- their multiple longitudinal that occur near the central charias teeth from ridges sp. the Clayton Limestone Unit can be

base on the lingual crown cusp face, sigmoidal central distinguished fromother taxa ofthe Clayton Limestone Unit in anterior cusp more central in based the absence of tooth, triangular cusp on longitudinal ridges on the lingual lateral tooth and the mesial and distal single cusplet on crown face and similar criteria utilized for Carcharias root lobes. In North America, teeth to this cf. whitei In Carcharias teeth belonging spe- general, sp. are most simi-

cies are most similarto those ofthe Carcharias holmdelen- lar to Carcharias samhammeri (Cappetta & Case, 1975) sis (Cappetta & Case, from the from 1975) Campanian- the Campanian-Maastrichtian ofNorth America {e.g. Maastrichtian and Sylvestrilamia teretidens (White, 1931) Gallagher, 1993; Hartstein etal., 1999;Becker, 2004). C. from the Paleocene and Eocene. Distinctions between C. samhammeri has not been reported from the Arkadelphia whitei and C. holmdelensis are based on the overall Formation.Distinctions larger between thesetwo species are subtle toothsize C.and more robust elements ofC.( whitei. and based cusp primarily on the overall much larger toothsize holmdelensis from the was previously reported nearby ofCarcharias sp. from the Clayton Limestone Unitalong

et Arkadelphia Formation by Becker al. Our withthe narrower crown base of (2006). the central cusp as seen in tentativeassignment ofthe Clayton LimestoneUnit teeth anterior teeth.

C. cf. whitei is to based on similarities between this Teeth the spe- belonging to genus Carcharias are common in cies and Carcharias teretidens, recently reassigned to the Paleogene of the Atlantic and Gulf Coastal Plains of

Sylvestrilamia by Cappetta & Nolf Both C. (2005). North America (Table 1). Our assignment ofthese Clayton whitei and S. teretidens have been identified from Limestone Unit teeth to Carcharias is based onthe overall

multiple locations in North America (e.g. Ward& Wiest, similaritiesof from many Paleogene species this genus re- 1990;Case, 1994; 1996; A oftooth Kent, 1999a). survey ported in sources such as Kent (1994). Reviewof bothhis- from various descriptions authors demonstrates that both torical and current North American literature demon- these similarand differences species are very may be more strates these similarities and the problems associatedwith chronostratigraphic than in Kent taxonomic classification morphological nature. based on isolatedteeth. Although

(1994) indicatedthat C. whitei before S. teretidens outside the ofthis appears scope paper, furtherstudy andtaxonomic in the Brightseat Formationofthe Chesapeake Region. revision is needed for Bay manyCenozoicNorth Americansand This formation is roughly equivalent in age to the Midway tiger to resolve these classification issues. & Group (Powars Bruce, 1999) and furthers our taxonomic association ofthe Clayton Limestone Unitteeth with C. cf. Family Cretoxyrhinidae Glickman, 1958 whitei. Genus Cretalamna Glickman, 1958

Carcharias Cretalamna sp. sp.

Figures 4.5a-6b Figures 4.7a-10a

Materialexamined— ANSP 23247, one anterior Material examined — ANSP tooth; 23249, one anterior tooth; ANSP lateral 23248, one tooth. ANSP lateral 23250, one tooth; ANSP 23251, one addi-

tional lateral tooth.

— Two teeth from Description 18-20 mm in total height; central cusp smooth, slender, and erect in anterior — Threeteeth from tooth; Description 13-14mm in total height; lingual face moderately convex and labial face central relatively cusp smooth, triangular and erect inanterior tooth, flat in anterior tooth; central more inclined cusp smooth, triangu- distally in lateral tooth; lingual face convex and lar, broad-based, and distally-inclined labiolingually labial face flat with smooth cutting edges; single, broad. -20-

Arkansas NJ CBR VA NC SCsc GA AL MS LA TX SD ND

Species

Odontaspis XXX X X

winkleri

2 1 Carcharias X1 1 XX XX' X1 X 2 XX 1

Cf. C. whitei

3 3 3 3 3 3 3 3 Carcharias X3X 3X 3X3X XX 3X XX 3X XX 3X XX 3

!£:sp.

3 3 3 2 2 2 Cretalamna I5 X 3 2 2X X2"X 3X X 3X X 2X X 2 XX 2

!E:sp.

2 AnomotodonAnomolodon XXX X X 2 2

novasnovus

Otodus X X X X XXX X

obliquus

Hypolophodon XXXX X X XXXX

sylvestris

2 2 2 2 2 2 2 2 Myliobatis X X X 2 X 2 X 2 X 2 XX X 2 X 2 XX 2 XX 2

dixonidixoni

Table 1. and Geographic distributionin North America ofClayton Limestone Unit sharks rays discussed in this report.

NOTES:

Acronyms: NJ - New Jersey; CBR - Chesapeake Bay Region; VA - Virginia; NC - North Carolina; SC - South Carolina; GA - Georgia;

AL - ; MS - Mississippi; LA - ; TX - ; SD - South Dakota; ND - North Dakota. References; NJ - Case, 1996;

CBR - Kent, 1994;Ward & Wiest, 1990;VA - Kent, 1999, Part 2; Kent, 1999, Part 3; NC - Case & Borodin,2000; SC - Purdy, 1998; GA

- Parmley et al., 2003; Case, 1981;AL - Thurmond& Jones, 1981; MS - Case, 1994; LA - Manning& Standhardt, 1986; TX - Stidham el al., 2008; SD - Cvancara & Hoganson, 1993; ND - Cvancara & Hoganson, 1993. Superscripts: 1 - listed as Carcharias teretidens; 2 -

Carcharias, Cretalamna, Anomotodonand Myliobatis genera occur in these states and are similar tothe Clayton LimestoneUnit speci- mens. However, no species names were assigned; 3 - Species similar to the Clayton LimestoneUnit specimens occur in these states.

mesialand distal lobes in anterior Cretalamna teeth from the triangular cusplets on root (Fig. 4.9-10). sp. Clayton

tooth; pair of triangular and divergent cusplets on lateral Limestone Unitcan be distinguished from those belonging teeth with secondary cusplets near edge of root lobe sub- to C. appendiculata by their overall larger size, narrower

stantially smaller; outer edges of root lobes relatively cusp base and well-definedbilobate roots.

straight and directly below toothcrown; shallow U-shaped These teeth differin their morphology from those tradition-

interlobe area; lingual root protuberance; no nutritive ally assigned to C. appendiculata and otherCretalamnaspe-

groove; holaucorhizous root. cies and subspecies infrequently reported from the Creta-

ceousand Paleogene in NorthAmerica such as C. biauricu-

Discussion — Cretalamna sp. teeth can be distinguished lata maroccana (Arambourg, 1935) (see Kent, 1994). C.

from most other teeth in the Clayton LimestoneUnit by the appendiculata is a well-reported species with a long chrono-

of broad and trian- - and worldwide presence asmooth faced, triangular cusp logical range ( Ypresian) a geo-

gular cusplets that are continuous with the cusp. These graphic distribution(Cappetta, 1987;Shimada, 2007). Such

smallerin total than Otodus is of Cretaceous - teethare substantially height along chronological range atypical any

obliquus Agassiz, 1843 from the Clayton Limestone Unit Paleogene chondrichthyan species and supports the need

whose lingual central cusp and cusplets are more convex for a revision of species assigned to this genus, particularly

and robust. Another Maastrichtian species found in the those surviving the K/P mass extinction.

Arkadelphia Formationthat shares some similar character-

istic Limestone Unit Cretalamna is Serrato- to Clayton sp. Family Mitsukurinidae Jordan, 1898 serrata (Agassiz, 1843); (Becker et al., 2006). Genus Anomotodon Arambourg. 1952

Teeth belonging to S. serrata display tooth asymmetry,

multiple diverging cusplets, smoothcrown faces, and ashort

nutritive 1991; Welton & Parish, groove (Landemaine, Anomotodonnovus (Winkler, 1874) None ofthese features is noted 1993; Kent, 1994). to oc- Figure 4.1 la-b LimestoneUnit cur in membersbelonging to Clayton Cre-

talamna in the Formation 1874 8. sp. Subsequent study Arkadelphia Oxyrhina nova Winkler, p. 7, pi. 2, fig.

ofHot Spring County, Arkansas since Becker et al., (2006)

of Material — indicates the occurrence Cretalamna appendiculata examined ANSP 23252, one lateral tooth. -21-

— lateral Description Single tooth 13 mm in total — height; Discussion Otodus obliquus teethare substantially lar-

central smooth, distally inclined with cut- and cusp complete ger more robust than any other species recovered from thatextend lobes and ting edges across root incipient cus- the Clayton Limestone Unit. the Additionally, presence of

plets; edge of mesial root lobe rounded and out- foramina projects multiple throughout the root lobes, more narrow

ward beyond oftooth distal root lobe edge crown; directly and divergent cusplets in the anteriortooth and distalhook

below tooth moderate with crown; lingual protuberance on the lateraltooth readily distinguish this species from weak nutritive well-defined dentalband on C. groove; lingual appendiculata. Other lateCretaceous species bear some

face; holaucorhizous root. resemblance O. to obliquus such as mantelli

although thisspecies became extinct inNorth America well

Discussion — The Anomotodon tooth be distin- before novus can the Maastrichtian(Shimada, 1997a). guished from other teeth in the Clayton LimestoneUnit by its smooth central cusp and complete cutting edges that extend across root lobes and incipient cusplets. The in-

cipient cusplets and complete cutting edges readily dis-

tinguish .A. novus from thoseofScapanorhynchus whose teethare well represented throughout the late Cretaceous by multiple species. Teeth from another late Cretaceous

Paranomotodon species, angustidens (Reuss, 1845) super-

resemble those of ficially A. novus. However, the overall tooth size ofP. angustidens is much smallerandthe central

is cusp more narrow, particularly near its base. Neither

Scapanorhynchus sp. nor P. angustidens have been identi-

fied from the Arkadelphia Formation(Becker etal, 2006). few Only a teeth ofA. novus were recovered at the Clay- ton Limestone Unit site. A. novus is also known to occur in the Atlantic Coastal Plain (Table 1) and apparently is less frequently encountered. Additionalspecies belonging to the genus Anomotodon that do not resemble A. novus may also be present in the late Cretaceous ofNorth America

(e.g. Case & Cappetta, 1997).

Family OtodontidaeGlickman, 1964

Genus Otodus Agassiz, 1843 5. Figure Teeth of Myliobatidae, chimaerid jaw fragmentand

vertebral centrafrom the Clayton LimestoneUnit, Hot Spring

County, Arkansas. 1- Hypolophodon sylvestris (ANSP Otodus obliquus Agassiz, 1843 23255); 2- Myliobatis dixoni(ANSP 23256); 3- Chimaerid Figures 4.12a-13b jaw fragment (ANSP23259); 4-5-Vertebralcentra (ANSP

Orientations: 1 = basal 23260-23261). a, 2a, 3a view; 1 b, 1843 Otodus obliquus Agassiz, 267-269, pi. 31,36, figs. = p. = = 2b, 3b occlusal view; 1c, 2c, 3c lateral; 4a, 5a arti- 22-27. cular surface view; 4b,5b = dorsolateral view; All scale

bars = 2.0 mm.

Materialexamined — ANSP 23253, one anterior tooth;

ANSP 23254, one lateral tooth. According to Cappetta (1987) and followed later by Kent

Otodus have arisen from (1994), may Cretalamnaand pos-

— Two teeth from 27-33 in total the Description mm sibly represents ancestor of some ofthe larger and later

central robust and anteriortooth Cenozoic lamniforms. O. height; cusp smooth; obliquus teeth are much larger triangular and lateraltooth with distal erect; hook; lingual than any encounteredin the nearby Arkadelphia Formation face convex and labialface flatwith smooth and cutting edges; (Becker et al, 2006), may represent a global trend enameloid withbroad wrinkles central base toward lamniforms near cusp on with greater total body lengths such labial face; single, well-definedtriangular and as those deducedfrom divergent teethtraditionally assigned to Car- cusplet in anterior and charodon tooth; broad, triangular divergent Agassiz, 1843; (e.g. Gotfried, 1996; cusplet with distinct notch on distal root lobe; root lobes Renz, 2002). incomplete; root lobe elongated and rounded in anterior tooth; root lobe straight and compressed in lateral tooth;

of root lobe below majority directly tooth crown; well- Superorder Batomorphii Cappetta, 1980 defined dental band on lingual face ofanteriortooth; multi- Order Myliobatiformes Compagno, 1973 foramina ple throughout root lobes; no nutritive groove; Family Dasyatidae Jordan, 1888 holaucorhizous root. Genus Hypolophodon Cappetta, 1980 -22-

tive and uniform thickness in Hypolophodon sylvestris White, 1931 grooves roughly as seen

Figures 5.1a-c lingual view. Similar Paleogene species from North

America include: Myliobatis striatus Buckland, 1837 and

1931 Hypolophodon sylvestris White, p. 70-73, figs. 94- Myliobatis latidens Woodward, 1889. Kent (1999b) indi-

115. cated that M. dixoni is the narrowest of these three species

and has a width four times that of its length. The Clayton

Material examined — ANSP 23255, one pavement Limestonetooth comparesfavorably to these dimensions crusher. and is the most commonly occurring batoid at this site.

Blain- Two additional genera of dasyatids, Aetobatus sp.

Description — Single tooth 4mm in dimension some greatest ville, 1816 and Rhinoptera sp. Cuvier, 1829 bear flat and (mesodistal width); crown relatively smooth, resemblance to M. dixonifromthe Clayton LimestoneUnit. bilobate hexagonal in occlusal view; basal ledge overhangs these notedto in the However, generaare appear early Eo- well-definedand located nutritive root; centrally groove; cene (ie.g. Cappetta, 1987; Weems, 1999). Similar teeth holaucorhizous root. from the late Cretaceous to M. dixoni are those from

Brachyrhizodus wichitaensisRomer, 1942.This species is not

— The tooth be Discussion Hypolophodon sylvestris can represented in the Arkadelphia Formation although it is fromotherbatoidteeth in the Lime- distinguished Clayton common in Campanian chondrichthyan faunas in North Unit its wide and stone by hexagonal outline, single deep America (e.g. Case & Schwimmer, 1988; Robb, 1989; nutritive and flat surface. The bears groove crown species Welton & Parish, 1993). Teeth from B. wichitaensis are

some resemblance to Pseudohypolophus mcnultyi wider and possess far fewer nutritive grooves thanthose

(Thurmond, 1971) which is well-known from the late ofM. dixoni.

Cretaceous of North America (e.g. Cappetta & Case,

1975; Case & Schwimmer, 1988; Hartstein etal., 1999; Order Chimaeriformes Becker et al., 2004), although it has not been documented

from the Arkadelphia Formation. H. sylvestris lacks the Chimaeridsp. indet. and labial more numerousand larger foraminaon the lingual Figures 5.5a-c flatter and root faces just below the crown foot, and has a

shallower nutritive than wider crown and groove P. Materialexamined—ANSP 23259 one incomplete (right mcnultyi. According to Kent (1999b), H. sylvestris is mandibular?) jaw fragment. known from the early Paleocene through early Eoceneof

the New Jersey and the Chesapeake Bay Region. A sur- Description — One incomplete (right mandibular?) jaw ofall available literature this is the vey regional suggests fragment with longest dimension6mm; osseous surfaces in first noted occurrence of the species in the Gulf Coastal occlusal, lateral and basal views; fragmentary tritors pres- Plain. ent.

Family Myliobatidae Bonaparte, 1838 Discussion — The occurrence ofchimaerids from the late Genus Myliobatis Cuvier, 1817 Cretaceous and Paleogene of North America has been

well-documentedfrom multiple locations by a numberof

species belonging to the Ischyodus and Edaphon Myliobatis dixoniAgassiz, 1843 genera (ie.g. Case, 1978;Case & Schwimmer, 1992; Hoganson & Figures 5.2a-c Murphy, 2002; Stahl & Parris, 2004; Parmley &

Cicimurri, 2005; Cicimurri et al., 2008). While the os- 1843 Myliobatis dixoni Agassiz, p. 319.

seous jaw fragment with tritors from the Clayton Limestone

crusher. Unitis characteristic ofmembersof this order, its fragmen- Materialexamined—ANSP 23256, one pavement

and ANSP additional tary nature precludes any higher order taxonomic classi- ANSP 23257 23258, two pavement

crushers. fication.To date, chimaeridshave been unreported in the

fossil literatureofArkansas but are known from the bor-

states ofTexas and Mississippi (Manning & Dock- Description — Largest tooth 17 mm in greatest dimen- dering 1992; McKinzie etal., 2001). sion (mesodistal width); crown mesodistally elongated, ery,

smooth, slightly arcuate, weakly convex and hexagonal;

numerous longitudinal ridges on vertical crown faces; basal Various species indet. - vertebralcentra

5.6a-7b ledge overhangs root with numerous, roughly equally- Figures

dimensional, deep nutritive grooves; root polyaula-

corhizous. Description — Two vertebralcentra with articularsurface 6

mm in diameter; articular surface circular with multiple

— dixoni concentric lamellaand vertebral Discussion The Myliobatis teeth can be distin- centrally-located birthmark;

guished from other batoid teeth in the Clayton Limestone rim well-defined; large foraminafor basal cartilage in dorso-

Unit by their mesodistally elongated form, multiple nutri- lateral view (see arrows); radial lamella in lamnoid-type -23-

in dorsolateralview; carcharhinoid-type vertebra teeth chondrichthyan well within this size range. Addi-

dorso-laterally compressed; lamnoid-type vertebra dorso- sediment tionally, samples throughout the entire site were

laterally elongated. collected and sieved. Similar techniques were employed at

our nearby Arkadelphia site where multiple examples of

Materialexamined—ANSP 23260, one ver- small lamnoid-type teeth belonging to Squatiniforms, Orectolobiforms, tebral centra; ANSP 23261, onecarcharhinoid-type vertebral and Carchariniformswere recovered (Becker et al, 2006).

centra. No indicativeof lag deposits taphonomic effects were en-

countered at the Clayton Limestone site. Individual teeth

Discussion — In additionto the chondrichthyan teeth, a were eroding directly out of the light-colored limestone,

number of and marl and lamnoid-type carcharhinoid-type verte- sandy marl intervals and are sporadically distri-

bral centra were also recovered from the Lime- buted. Such known Clayton lags are to concentrate chondrichthyan

stone Unit. Lamnoid-type vertebral centra have teeth from all many sizes, including those less than 1.0 cm, and septa and large, basidorsal and basiventral foramina paired may bias age, abundanceand palecological interpretations while carcharhinoid-type vertebralcentra lack Case & paired foramina, {e.g. Schwimmer, 1988; Eaton etal., 1989; Ward are more solid, and lack distinctive septa (Shimada, 1997b; & Weist, 1990; Manning & Dockery, 1992; Rogers & Kid- Blanco-Pinonet al, Becker Association 2005; etal, 2008). well, 2000; Burris, 2001; Becker etal., 2010a). Additional of isolated chondrichthyan vertebrae with any particular bulk result in the of few sampling may recovery a more species is problematic as demonstratedby the well-known chondrichthyan with species small teeth belonging to the late Cretaceous lamniform. In this sp. spe- above mentionedorders. However, itis evident by compari- cies, teeth and associated teeth tissues those of 1am- are a son to other contemporaneous formations from single loca- niform but vertebral centra similar are more to those of a tions, that the Paleocenechondrichthyan record in North carcharhiniform (Shimada & Cicimurri, Becker et America 2005; al, is limited in species diversity when compared

2008). In this regard, the Clayton Limestone Unit vertebrae to the late Cretaceous and Eocene. are no and little is known about the skeletal exception an- In the GulfCoastal few exist Plain, reports on the occur- atomy ofPaleogene from chondrichthyans North America. rence of Paleocene chondrichthyans. To date, these in-

The presence of vertebral clude late carcharhinoid-type centra may a Paleocene-early Eocene assemblage from also that sharks suggest Paleogene belonging to car- Mississippi and Alabama(Thurmond & Jones, 1981; Case, in charhiniforms occur the Limestone al- and Clayton Unit, 1994), a preliminary report of a late Paleocene fauna though none were recovered this research from during project. the Calvert BluffFormation of Texas (Stidham &

This interpretation is supported by the ofmulti- Additional appearance Janus, 2008). chondrichthyan reports from the of carcharhiniforms in ple genera North Americaand glo- GulfCoastal Plain states are from the Eocene or younger bally during the Paleocene (e.g. Gurr, 1963; Arambourg, (e.g. Manning & Standhardt, 1986; Case & Borodin, 2000; 1952; Cappetta, 1987; Kent, 1994). Hulbert, 2001;Parmley etal, 2003). In this regard, theClay- Limestone ton chondrichthyans provide another important

snapshot ofspecies diversity directly above the K/P boun- Discussion dary and during the Paleocene ofthe GulfCoastal Plain.

Composition ofthe Limestone Clayton chondrichthyan Paleoecology, faunalturnover and extinction assemblage The limestone, marl and sandy marl ofthe Clayton Lime- As indicated in the discussions the above, chondrichthy- stone site along with the co-occurring invertebrate fossils ans recovered from the Clayton Limestone site are of shallow represent typical a tropical seaway that would species widely-known from North America (Table 1). Ab- have covered southwestern Arkansas duringthe Late Cre- sent from the Limestone site Clayton are chondrichthyan taceous and Paleogene. The Clayton Limestone chondrich-

to orders species belonging including: Hexanchiformes, are thyans represented by pelagic apex predators, shallow

Squaliformes, Squatiniformes, Orec- forms and Heterodontiformes, water piscivorous durophagous shell-crushers, as tolobiformesand Carchariniformes. InNorth evidenced tooth America, spe- by morphology (Figs. 4-5). Such a di- cies belonging to these orders have been documented else- of modes verse range feeding are typical ofother contempo- where duringthePaleocenebut are few in number Ward raneous (e.g. chondrichthyan assemblages throughout North _ & Weist, 1990; Case, 1994). Kent indicated that America and (1994) reflect analogous shallow marine and near- such be encountered due species may infrequently to shore ecosystems. small size, species rarity, and offshore pelagic life modes. No Cretaceous-Paleogene chondrichthyans indicative of

It is important to note that teethfrom most North Ameri- brackish or transitional marine conditions such as can Paleocene species belonging to the above mentioned Myledaphus bipartitus Cope, 1875b (e.g. Bryant, 1989; orders are less than 1.0 cm in total the height. Thus, appar- Wroblewski, 2004) were recovered at the Clayton Lime- ent ofthese rarity chondrichthyan species at some localities stone site. However, evidence also indicates that

be in the result of may part sampling techniques. Our bulk Arkadelphia Formation-Midway Group shoreline had sampling techniques both on site and in the laboratory fluvial connections documented nearby as by the presence utilized sieves with mesh sizes of of capable recovering fragments of wood and plants and osteichthyans be- -24-

longing tothe Acipenseridae and Lepisosteidae (Becker et throughout North America and elsewhere. Teeth from the

Carcharias also al, 2010b). Osteichthyans from these two families have genera Odontaspis and are morphologically

inhabit similarwith dentitionsevolved for both fossil and modemrepresentatives known to a very grasping piscivorous

life modes 1965; Welton & Parish, broad range of salinities. (Applegate, 1993).

The of in the Paleocene also appearance O. obliquus

demonstrates of across Squatina hassei replacement pelagic apex predators the K/P As indicated in the discussions Ginglymostoma lehneri boundary. above,

Plicatoscyllium derameei tooth morphology in this species is similarto thatof C.

Ondontaspis aculeatus Odontaspis winkleri mantelli although this species became extinct in the early Carcharias cf.cf. holmdelensis Carcharias cf. whitei Carcharias Campanian (Shimada, 1997a; 2007).

Serratolamnaserrataserrata Carcharias sp. The geographic proximity ofthe Arkadelphia Formation- Cretalamna appendiculata Cretalamna sp. Clayton Limestone Unit sites offers a unique opportunity Anomotodon novus Squalicorax kaupi novus to sample extinction, replacement and survivorship in conse- Galeorhinus giradoti Otodus obliquus cutive formationsthat cross the most well-studied mass Rhinobatoscasiericasieri Hypolophodon sylvestris extinction event in earth history. These sites support avonicola Myliobatis dixoni global studies (e.g. Kriwet & Benton, 2004) that indicate Ischyrhiza mira

an evolutionary bottleneck in chondrichthyan diversity sp.

Schizorhiza cf. stromeri occurred during the end-Cretaceous mass extinction.

that chon- cf. vermiculata Comparison ofboth assemblages also suggests

Raja farishi drichthyan diversity remained low in the Paleocene until

Rhombodus binkhorsti radiation of and marine mammals in the middle

Dasyatis sp. Cenozoic provided a resource base necessary for their di-

versification.Further investigation is necessary to docu- Table 2. reported from the Arkadelphia Forma- Chondrichthyans ment the exact and of both timing age chondrichthyan as- tion (left) and Clayton Limestone Unitofthe Midway Group, semblages relative to the K/P boundary. However, the cata- (right) Hot Springs County, Arkansas. Occurrence data for strophic effects ofthe of the K/P boundary mass extinction the ArkadelphiaFormation is from Becker et al (2006). in southwestern Arkansas seem apparent.

A comparison between chondrichthyans recovered fromthe Acknowledgments Arkadelphia Formationand Clayton Linestone Unit in Hot

Spring County is given in Table 2. Only three genera, We thank the following individuals for their contribu- Odontaspis, Carcharias, and Cretalamna,represented by tions to this study and manuscript: R. Farmer introduced different Maastrichtian and Paleocene species, occur in of us to his field site in the Clayton Limestone Unit the both assemblages. The most striking differences between Midway Group, Hot Spring County, Arkansas. D. Wright, A. the two assemblages occur in the Rajiforms, particularly DeAngelo, and J. DeAngelo and C. Mallery provided assis- those belonging to the . All species belong- tance with field work and fossil collection. T. Daeschler and ing tothe genus Rhombodus family Sclerorhynchidae from the Academy ofNatural Sciences Philadelphia estab- are known to go extinct at the K/P boundary (Kriwet & lished the repository for our specimens. The original manu- Benton, 2004). In their analysis of chondrichthyan di- efforts of script was greatly improved by the review S. the K/P Kriwet & versity across boundary, Benton in Tracey and D. Ward. This research was supported part (2004) also indicatedthat six other chondrichthyan fami- for Research from William Paterson by a Center grant lies go extinct along with genera , University to M. Becker. Paranomotodon, Archaeolamna and Squalicorax at this

and well-known boundary. These families genera are

throughout the Campanian-Maastrichtian of North References Americawith Squalicorax kaupi occurring in the Arkadel-

phia Formation. les 1833-1844. Recherches sur 1-5,1, similar Agassiz,L. poissonsfossiles. Based on tooth morphology comparison between de 420 pp. Imprimerie Petitpierre, Neuchatel and Soleure, LimestoneUnit Arkadelphia Formation and Clayton spe- , 5 vols. of cies included in the discussions above, many these ex- Applegate,S.P. 1965.Tooth terminology andvariation in sharks tinctions the and levels at genus species were replaced by with special reference to the sand . Carcharias taurus with similar adaptations. Pavement crushers be- groups Rafmesque. Los Angeles County Museum, Contributions in

to below and above the K/P boun- longing Myliobatiforms Science, 86,1-18. share similar dary morphological characteristics, although Arambourg, C. 1935. Note preliminaire sur vertebras fossiles des Such similarities teeth from M. dixoniare generally larger. phosphates du Maroc. Bulletin de la Societe Geologique de

ideally evolved toexploit the abundanceofbenthic mollusks , 5,413-440.

C. 1952. Les vertebras fossiles des de andinvertebratesfoundthroughout the shallow marineenvi- Arambourg, gisements phos- (Maroc-Algerie-Tunisie). Service Geologique du ronments during the Maastrichtian-Paleoceneand found phates -25-

Maroc. Notes et Memoires, 92,1-372. LauderdaleCounty, Mississippi. PalaeonlographicaAbt. A, Chamberlain Becker, M.A., Jr., J.A. & Terry, D.O. 2004. Chon- 230, 97-138.

drichthyans fromthe F Memberofthe FoxHills airpoint Forma- Case, G.R. 1996. A new selachian fauna from the Lower

tion (Maastrichtian), Meade South Dakota. Journal County of Homerstown Formation (Early Paleocene, Montian) of VertebratePaleontology, 780-793. Monmouth 24, County,New Jersey,Palaeonlographica Abt.A,242, Becker, M.A., Chamberlain Jr., J.A. & Wolf, G. 2006. Chon- 1-14.

from the Formation drichthyans Arkadelphia (Upper Creta- Case, G.R. & Schwimmer, D.R. 1988. LateCretaceous fish from the late ofHot ceous: Maastrichtian) SpringCounty, Arkansas. Jour- Blufflown Formation(Campanian)in western Georgia.Journal nal ofPaleontology, 80, 700-716. ofPaleontology, 62,29-301.

M R. Becker, A., Chamberlain, & Chamberlain Jr., JA. 2008. Large Case, G.R. & Schwimmer, D.R. 1992. Occurrence of the chi-

carcharhinoid-typeshark vertebrae in the Upper Cretaceous of maeroid Ischyodus bfurcatus Case in the Cusseta Formation New evidence for anacoracid Northeastern Jersey: an origin. (Upper Cretaceous, Campanian) of western Georgia and its and Geology EnvironmentalSciences, 30, 118-129. distribution.Journal ofPaleontology, 66, 347-350. Becker, M.A., Wellner, C. & Chamberlain R., Malleiy, Jr., J.A. Case, G.R. & Cappetta, H. 1997. A new selachian faunafrom the 2010a. from Chondrichthyans the Lower Perron Sandstone late Maastrichtian of Texas. Munchner Geowissenschqften Member of the Mancos Shale (Upper Cretaceous: Middle Abhandlungen, 34,131-189.

Turanian) of Emery and CarbonCounties Utah,USA. Journal Case, G.R. & Borodin, P.2000. A MiddleEocene selachin fauna

ofPaleontology, the 82,248-266. from Castle Hayne Limestone Formation of Duplin C. & Chamberlain Becker, M., Mallery, Jr., J.A. 2010b. Osteich- County, NC. Munchner Geowissenschaften Abhandlungen.

thyans fromthe ArkadelphiaFormation(LateMaastrichtian)of 39,17-32.

Hot USA. Spring County, Arkansas, Journal of Vertebrate Cicimurri, D.G., Parris, D.C. & Everhart, M J.2008. Partial dentition 30,1019-1036. Paleontology, of a chimaeroid fish (Chondrichthyes, Holocephali) from the Berg, L.S. 1958.System rezenten undfossilen und Fisch. Cretaceous Fischartigen Upper Niobrara ChalkofKansas, USA. Journal of

Hochschulbucherjur Biologic, Berlin, 4, 1-310. VertebratePaleontology, 28, 34-40. H. de 1816.Prodrome d’unenouvelle distribution Blainville, syste- Compagno,L.J.V. 1973.Interrelationshipsofliving elasmobranchs. du . Bulletindes Sciences la matique regne par Societe Journalofthe LinneanSociety. Zoology, 53, 63-98.

Philomatique deParis, 8,105-125. Cope, EX). 1875a. Synopsis ofthe Vertebrataof the of

Blanco-Pinon,A., K. & G. Shimada, Gonzalez-Barba, 2005. Lam- CumberlandCounty, New Jersey. Proceedings ofthe Ameri- noid vertebraefromthe Formation AguaNueva (UpperCreta- can Philosophical Society, 14,361-364.

Lower-Middle NE ceous: Turanian), Mexico. Revista Mexi- Cope, EX). 1875b. The Vertebrateofthe Cretaceous formationsof

cana de Ciencias Geologicas 22,19-23. the West Reportof the UnitedStates Geological Survey ofthe C.L. 1832-1841. Bonaparte, Iconografia dellafaunaItalica, per Territories, 2,1-303.

le classi animali vertebrati. 3 quattro degli (Pesci). 78 Cushman, JA. 1949. The foraminiferal faunaofthe Upper Creta- Rome. pls.Tipographia Salviucci, ceous Arkadelphia Marl ofArkansas. U.S. Geological Survey W. 1837. Buckland, GeologyandMineralogy consideredwithspecial Professional Paper, 221,1-19.

reference to natural theology. William London 1- Cuvier, G. 1817.Le animal distribue Pickering, Regne d ’apres sonorgani- 580. servir de I sation, pour base a ’histoirenaturelledes animaux

Burris, J.H. 2001. Reworked Cretaceous elasmobranchteeth and d'introduction 4 et a I'anatomic comparee. vols. Deterville,

Hanna provenance ofthePaleocene Formation(HannaBasin, Paris.

Wyoming). Rocky Mountain 37-48. G. 1829.Le Geology, 36, Cuvier, Regne animaldistribue d'apres son organisa- L J. 1989.Non-Dinosaurian lower Bryant, vertebrates across the tion, pour servir de base a/’histoirenaturelledes animaux et

in boundary northeasternMontana.Geo- d’introductiona I ’anatomie 406 Cretaceous-Tertiary comparee. 2(2) xv, pp. De-

logic Science. University ofCaliforniaPublications, 134,1- terville, Paris.

107. Cvancara, A. & Hoganson, J.M. 1993. Vertebrates ofthe Cannon-

Cappetta,H. Les Cretace 1980. selaciens du superieur du Liban. II. ball Formation(Paleocene) in North and South Dakota. Jour-

Batoides. Abt. A, 149-229. Palaeonlographica 168, nal ofVertebrate Paleontology, 13,1-23. Cappetta, H. 1987. andCenozoicElas- Chondrichthyesn, Eastman, C.R. 1901. Pisces. Pp. 98-113,pls.12-15 in: Clark, W.B. mobranchii. In: Schultze H.P. Handbook (ed.). of & Martin, G.C. (eds.). The Eocene deposits of Maryland. paleoichthyology. Vol. 3B. 193 Gustav Fisher pp. Verlag, Maryland Geological Survey, Stratigraphic Memoir,

Stuttgart. Baltimore.

H. Cappetta, & Case, G.R. a 1975. Contributions 1’etudedes Eaton, J.G., Kirkland, JJ. & Doi, K. 1989. Evidence of reworked

selaciens du Monmouth - Cretaceous groupe (Campanian Maastrichtian) fossils andtheirbearingon theexistence of Tertiary du New Abt. Jersey. Paleontographica A, 5,1-146. dinosaurs.Palaios, 4,281-286. Cappetta,H. & Nolf. D. 2005. Revision de quelquesOdontaspidi- Fowler, H. 1911. A descriptionof the fossil fish remains ofthe Creta-

dae du Paleoceneet del’Eocene Eocene (Neoselachii: Lamniformes) du ceous, and Mioceneformations ofNew Jersey. New

Bassin de lamer du Nord. Bulletin de /Institul des Sciences Royal Jersey GeologicalSurvey Bulletin, 4,1-192. Naturelles de Belgique. Sciences de la 75,237-266. Terre, Freeman, T. 1966. Fossils of Arkansas. Arkansas Geological Case, G.R. 1978. Ischyodus bifurcatus, anew species of chimaeroid CommissionBulletin, 22,1-53. fish from the Upper Cretaceous ofNew Jersey. Geobios, 11. Gallagher, W.B. 1993. The Cretaceous-Tertiary mass extinction

21-29. in event the northern Atlantic Coastal Plain. The , 5, G.R. Case, 1981.Late Eocene selachians from south-central Geor- 75-154.

gia. PalaeonlographicaAbt. A, 176, 52-79. Glickman, L.S. 1958.Rates ofevolution in lamnoid sharks. Doklady G.R. Fossil Case, 1994. fish remains fron the Late Paleocene Akademii Nouk, 123,568-672.

Tuscahomaand Early Eocene Bashi FormationsofMeridian, L.S. Sharks Glickman, 1964. ofthe Paleogeneandtheirstratigraphic -26-

Moscow. Cretaceous 745-775. significance. 229 pp. Nauka Press. Research, 19,

Gotfried, M.D., Compagno, L.V.J. & Bowman, S.C. 1996. Size Kriwet, J. & Benton, MJ. 2004. Neoselachian (Chondrichthyes,

and skeletal anatomy of the giant “Megatooth” shark Car- ) diversity across the Cretaceous-Tertiary boun-

charodonmegalodon.Pp. 55-66 in: Klimley, A.P., & Ainley, dary. Palaeogeography,PalaeoclimatologyandPalaeoecology,

D.G. (eds.), Great white sharks: The biology of 214,181-194.

carcharias. Academic Press, San Diego. Landemaine, 0.1991. Selaciens nouveaux du Crctacc superieur du

Gurr, P.R. 1963.Anew fish fauna from theWoolwich Bottom Bed Sud-Ouestde la France. Quelques apports a la systematique des

(Spamacian) ofHeme Bay, Kent. Proceedings of the Geolo- elasmobranches. Societe Amicale des Geologues Amateures,

' gists Association, 47,419-447. Museum ofNatural History, Paris, 1, 1-45.

Haley B.R., Glide, E.E., Bush, W.V., Clardy, B.F., Stone,C.G., Leidy, J. 1877. Description ofvertebrate remains, chiefly from the

Woodward,M.B. & Zachry, D.L. 1993. Geologic MapofAr- phosphate beds of South Carolina. Journalof theAcademy of

. 1:500,000scale. Arkansas Geological Commission. Natural Sciences ofPhiladelphia, 8,209-260.

Hartstein, E, Decina, L. & Keil, R. 1999.A Late Cretaceous (Severn Leriche, M. 1905. Les poissons tertiaires de la Belgique. II. Les

Formation) vertebrateassemblage fromBowie,Maryland. The poissons . Memoire du Musee Royal d’Histoire Na-

Mosasaur, 6,17-24. turelle de Belgique, 11,49-228.

Hay, O.P. 1902. On a collection of Upper Cretaceous fishes from Liddicoat, J.C., Hazel, J.E. & Brouwers, E.M. 1981. Magnetostrati-

Mount Lebanon, Syria, with descriptions offour new genera graphyofUpperCretaceousdepositsin southwesternArkansas

and nineteennew species. Suitetin oftheAmerican Museum of and northeastern Texas. American Association ofPetroleum

Natural 395-452. Geologists Bulletin, 65,764-765. History, 19,

Hoganson, J. & Murphy, E. 2002. Marine Breien Member Manning, E.M. & Dockery, D.T. 1992. A guideto the Frankstown

(Maastrichtian) ofthe Hell Creek Formationin North Dakota; vertebrate fossil locality (Upper Cretaceous), Prentiss County,

in: Environmental stratigraphy, vertebrate fossil record, and age. Pp. 247-269 Mississippi. Mississippi Department of

Hartmann, J.H., Johnson,K.R. & Nichols, D.J. (eds.). The Hell Quality, Office ofGeology Circular, 4, 43 pp.

Creek Formation and the Cretaceous-Tertiary boundary in Manning, E. & Standhardt, B. 1986.Late Eocene sharks and rays of

the Northern Great Plains: anintegratedrecord ofthe endof Montgomery Landing,Louisiana.Pp. 133-161 in: Schiebout J.

the Cretaceous. Geological Society ofAmerica, Special Paper & van den Bold, W. (eds), MontgomeryLanding site, marine Eo-

361. cene (Jackson) ofcentra! Louisiana. GulfCoast Association of

Baton Hulbert, R.C. (ed.). 2001.Fossil vertebratesofFlorida.350 pp. Uni- Geologic Societies, SymposiumProceedings, Rouge.

versity ofFloridaPress, Gainesville, Florida. Marsh,O.C. 1869.Notice of somenew Tatiary andCretaceous fishes.

Huxley, T.H. 1880.Ontheapplication onthe lawsofevolutiontothe Proceedingsof theAmerican Associationfor the Advancement

arrangementof the vertebrata and moreparticularly ofthe Mam- ofScience, 18, 227-230.

malia. Zoological Society ofLondon, Scientific Memoirs, 4, McFarland, J.D. 1998.Stratigraphic Summaryof Arkansas. Arkansas

457-472. Geological Commission Information Circular, 36, 1-38 (re-

Jones,E.L. 1962.Palynology oftheMidway-Wilcoxboundary in vised 2004).

south-central Arkansas. GuffCoastAssociation ofGeological McKinzie, M.G., Morin, R. & Swiatovy, E. 2001. Fossil collec-

Societies Transactions, 12, 285-294. tor’s guidebooktotheNorth SulfurRiver. OccasionalPapers

Jordan,D.S. 1888.A manualofthe vertebrateanimals ofthe north- ofthe DallasPaleontologicalSociety, 4,1-119.

the ern , including the district north and east of the Meyer, R.L. 1974.LateCretaceous elasmobranchs from Missis-

Ozark mountains, south ofthe Laurentian hills, north of the sippi andEast TexasEmbaymentsof theGulfCoastalPlain Un-

southern boundaryofVirginia andeast ofthe MissouriRiver, published Ph.D. dissertation. Southern Methodist University,

inclusive marine 5* ed. 375 A.C. of species. pp. McClurg, Dallas, Texas, 419 pp.

Chicago. Muller, J. & Henle, F.J.G. 1838-41. Systematische Beschreibung

Jordan, D.S. 1898.Description ofa species offish (Mitsukurina derPlagioslomen. Veit und Comp., Berlin, xxii, 200 pp., 60

owstoni) from Japan,thetype ofa distinct family oflamnoid pis.

sharks. Proceedings ofthe CaliforniaAcademy ofSciences, Parmley, D., Cicimurri, DJ. & Campbell, B. 2003. Late Eocene

3,199-202. sharks ofthe Hardie Mine local fauna ofWilkinson County,

Kent B.W. 1994. Fossil sharks of the ChesapeakeBay region 146 Georgia. GeorgiaJournalofScience, 61, 153-179.

Rees D. & D J. 2005.First recordof chimaeroidfish pp. Egan and Boyer Inc., Baltimore, Maryland. Parmley, Cicimurri, a

Kent, B.W. 1999a. Sharks from theFisher/Sullivan site. Pp. 11-38 from the Eocene ofthe southeastern United States. Journalof

in: Weems, R.E. & Grimsley, G.J. (eds.), Early Eocene verte- Paleontology, 79,1219-1221.

brates andplantsfrom the Fisher/Sullivan site (NanjemoyFor- Pitakpaivan, P. & Hazel, J.E. 1994. Ostracods and chronostra-

mation) StaffordCounty, Virginia. Virginia Division ofMin- tigraphic position ofthe Upper Cretaceous ArkadelphiaFor-

eral Resources Publication 152. mation ofArkansas. Journal ofPaleontology, 68, 111-122.

Kent, B.W. 1999b. Rays from the Fisher/Sullivan site. Pp. 39-52 Powars, D.S. & Bruce, T.S. 1999. The effects ofthe Chesapeake

in: Weems, R.E. & Grimsley, G.J. (eds.). Early Eocene verte- Bay impact crater onthe geological framework and correlation

brates andplantsfrom the Fisher/Sullivan site (Nanjemoy For- ofhy drogeologicunits oftheLower York-JamesPeninsula, Vir-

mation) StaffordCounty, Virginia. Virginia Division ofMin- ginia. US. GeologicalSurveyProfessionalPaper, 1612,1-82.

eral Resources Publication 152. Purdy, R.W. 1998. Chondrichthyan fishes from the Paleocene of

Kennedy, W.A., Landman, N.H., Christensen,W.K., Cob- South Carolina. Transactions oftheAmerican Philosophical Soci-

ban,W.A. & Hancock, J.M. 1998. Marine connections in ety. 88.122-146.

North America during the late Maastrichtian: Palaeoge- Rafinesque, C.S. 1810. Caraterri di alcuni nuovi generi e nuove

ographic and palaeobiologic significance of Jeletzkytes ne- speciedi animali epicmte della Sicilia, con varie osservazioni

i brascensis zonecephalopodfauna from the Elk Butte Mem- sopra medisima. 105 pp. Palermo, Italy.

ber ofthe Pierre SE South Dakota and NE Nebraska. M. 2002. the Himter. 159 Shale, Renz, Megalodon:Hunting pp. PaleoPress, -27-

Lehigh Acres, Florida.

Geonostische skizzen Reuss, A.E. 1845. aus Bbhmen. 304pp. Pra-

gue.

Robb, A.J. III. 1989. The Upper Cretaceous (Campanian, Black

Creek Formation) fossil fish fauna of Phoebus Landing,

BladenCounty, North Carolina. The Mosasaur, 4,75-92.

Rogers, R.R. & Kidwell, S.M. 2000. Associations of vertebrate

skeletal concentrations and discontinuity surfaces in terrestrial

and shallow marinerecords; A test in the Cretaceous of Mon-

tana. JournalofGeology, 108, 131-154.

Romer, A. 1942. Notes on certain American Paleozoic fishes.

American JournalofScience, 204,216-228.

Shimada, K. 1997aSkeletalanatomy of the Late Cretaceous Lamni-

form shark: Creloxyrhinamantelli, from the Niobrara Chalk in

Kansas .JournalofVertebratePaleontology, 17,642-652.

Shimada, K. 1997b.Gigantic lamnoidshark vertebra from the Lower

Cretaceous Kiowa Shale ofKansas. JournalofPaleontology, 71,522-524.

Shimada, K. 2007. Skeletal and dentalanatomy oflamniformshark,

Cretalamnaappendiculata, from Upper CretaceousNiobrara

Chalk ofKansas. Journalof Vertebrate Paleontology, 27.584

-602.

Shimada, K. &.Cicimurri, DJ. 2005. Skeletalanatomy ofLate Creta-

ceous shark.Squalicorax (Neosalachii; Anacoracidae). Palae-

ontologische Zeitschrift, 79,241-261.

Smith, A.G., Smith, D.G. & Funnel!, B.M. 1994. Atlas of Mesozoic

andCenozoic coastlines. 109 pp. Cambridge University Press,

Cambridge.

Stahl, B.J. & Parris, D.C. 2004. The complete dentition of Ed-

aphodon mirificus (Chondrichthyes: Holocephali) from a sin-

gle individual. Journal ofPaleontology, 78,388-392.

Stidham. T.A. & Janus, T.A. 2008. New vertebrates from the

Paleogene of eastern Texas. Transactions of the GulfCoast

Association ofGeological Societies, 58, 853-855.

Thurmond, J. 1971.Cartilaginous Fishes ofthe Trinity Group and

Related Rocks (Lower Cretaceous) ofNorth Central Texas.

Southeastern Geology, 13, 207-227.

Thurmond, J-T. & Jones,D.E. 1981.Fossil vertebrates ofAlabama.

244 pp. University ofAlabama Press. Tuscaloosa.

Ward J. & Wiest, R.L. 1990. A checklist of Paleocene and Eo-

cene sharks and rays (Chondrichthyes) from the Pamunkey

Group, Maryland and Virginia, USA. Tertiary Research, 12,

81-88.

Welton,BJ.&Parish.R.F. 1993.The collector's guidetofossil sharks

and the Cretaceous andraysfrom the Cretaceous of Texas. 204 pp. Before Time,

Lewisville, Texas.

White, E.I. 1931. The Vertebrate Fauna of the English Eocene.

Vol. I. From the Thanet Sands to the Basement Bed of the

London Clay. 123 pp. British Museum ofNatural History, London.

T.C. 1874. Deuxieme Winkler, mcmoire sur des dents de pois-

sons du terrain Bruxellien. Archives du Musee Teyler, Haar-

Netherlands. 33 lem, Preprint: pp.

Woodward,A.S. 1889. Catalogue of the fossilfishes in the British

Museum ofNatural Museum. 1,474pp. British History, Lon-

don.

Wroblewski, A.F. J. 2004. New selachian paleofaunasfrom fluvial

deposits ofthe Ferris and Hanna Formations (Maastrichtian-

Selandian: 66-58 Ma), southern Wyoming. Palaios, 19, 249-

258.