View, CMM-I-2126

SYSTEMATICS AND PALEOECOLOGY OF MIOCENE PORTUNID AND

CANCRID DECAPOD FOSSILS FROM THE ST. MARYS FORMATION,

MARYLAND

A thesis submitted

To Kent State University in partial

Fulfillment of the requirements for the

Degree of Master of Science

Heedar Bahman

August, 2018

Except for previously published materials

Thesis written by

Heedar Bahman

B.S., Kuwait University, 2011

M.S., Kent State University, 2018

Approved by

Rodney M. Feldmann , Ph.D., Advisor

Daniel Holm , Ph.D., Chair, Department of Geology

James L. Blank , Ph.D., Dean, College of Arts and Sciences

TABLE OF CONTENTS

TABLE OF CONTENTS ...... iii

LIST OF FIGURES ...... iv

LIST OF TABLES ...... vii

ACKNOWLEDGMENTS ...... viii

SUMMARY ...... 1

INTRODUCTION ...... 2

GEOLOGICAL SETTING ...... 5

METHODS ...... 7

SYSTEMATIC PALEONTOLOGY ...... 8

DISCUSSION ...... 27

CONCLUSIONS...... 32

APPENDIX ...... 33

FIGURES ...... 34

REFERENCES ...... 52

iii LIST OF FIGURES

Figure Page

1 n. sp. 1, dorsal view, CMM-I-2126 ...... 34

2 n. sp. 1, dorsal view, CMM-I-4310 ...... 34

3 n. sp. 1, ventral view, CMM-I-4310 ...... 34

4 n. sp. 1, dorsal view, CMM-I-4305 ...... 35

5 n. sp. 1, dorsal view, CMM-I-2987 ...... 35

6 n. sp. 1, dorsal view, CMM-I-3833 ...... 35

7 n. sp. 1, dorsal view, CMM-I-4306 ...... 36

8 n. sp. 1, dorsal view, CMM-I-3657 ...... 36

9 n. sp. 1, dorsal view, CMM-I-4307 ...... 36

10 n. sp. 1, ventral view, CMM-I-4307 ...... 37

11 n. sp. 1, dorsal view, CMM-I-3806 ...... 37

12 n. sp. 1, dorsal view, CMM-I-3970 ...... 37

13 n. sp. 1, dorsal view, CMM-I-3796 ...... 38

14 n. sp. 1, dorsal view, CMM-I-4311 ...... 38

15 n. sp. 1, dorsal view, CMM-I-2863 ...... 38

16 n. sp. 1, dorsal view, CMM-I-3954 ...... 39

17 n. sp. 1, ventral view, CMM-I-3954 ...... 39

18 n. sp. 1, dorsal view, CMM-I-4309B ...... 39

iv 19 n. sp. 1, dorsal view, CMM-I-4309A ...... 40

20 n. sp. 1, dorsal view, CMM-I-4308 ...... 40

21 n. sp. 1, dorsal view, CMM-I-4312 ...... 40

22 Necronectes drydeni, dorsal view, CMM-I-231 ...... 41

23 Necronectes drydeni, ventral view, CMM-I-231 ...... 41

24 Necronectes drydeni, dorsal view, CMM-I-4317 ...... 41

25 Necronectes drydeni, ventral view, CMM-I-4317 ...... 42

26 Necronectes drydeni, dorsal view, CMM-I-4313 ...... 42

27 Necronectes drydeni, ventral view, CMM-I-4313 ...... 42

28 Necronectes drydeni, dorsal view, CMM-I-4318 ...... 43

29 Necronectes drydeni, ventral view, CMM-I-4318 ...... 43

30 Necronectes drydeni, dorsal view, CMM-I-4320 ...... 43

31 Necronectes drydeni, ventral view, CMM-I-4320 ...... 44

32 Necronectes drydeni, dorsal view, CMM-I-4319 ...... 44

33 Necronectes drydeni, ventral view, CMM-I-4319 ...... 44

34 Necronectes drydeni, dorsal view, CMM-I-4314 ...... 44

35 Necronectes drydeni, ventral view, CMM-I-4314 ...... 45

36 Necronectes drydeni, dorsal view, CMM-I-3920 ...... 45

37 Necronectes drydeni, ventral view, CMM-I-3920 ...... 45

38 Necronectes drydeni, dorsal view, CMM-I-4316 ...... 46

v 39 Necronectes drydeni, ventral view, CMM-I-4316 ...... 46

40 Necronectes drydeni, dorsal view, CMM-I-4043 ...... 46

41 Necronectes drydeni, dorsal view, CMM-I-2941 ...... 47

42 Necronectes drydeni, ventral view, CMM-I-2941 ...... 47

43 Necronectes drydeni, dorsal view, CMM-I-3931 ...... 47

44 Necronectes drydeni, ventral view, CMM-I-3931 ...... 47

45 Necronectes drydeni, dorsal view, CMM-I-3996 ...... 48

46 Necronectes drydeni, ventral view, CMM-I-3996 ...... 48

47 Cancer borealis, dorsal view, CMM-I-2796 ...... 48

48 Cancer irroratus, dorsal view, CMM-I-2616 ...... 48

49 n. sp. 2, dorsal view, barnacles attached to the left side of the carpace, CMM-I-4014 ...... 49

50 n. sp. 2, ventral view, showing the left cheliped, CMM-I4014 ...... 49

51 Callinectes sapidus., dorsal view, CMM-I-3688 ...... 50

52 Callinectes sapidus, ventral view, female pleon, CMM-I-3688 ...... 50

53 Callinectes sapidus., dorsal view, CMM-I-3688 ...... 51

54 Calinectes sapidus., ventral view, immature female pleon, CMM-I-3688 ...... 51

vi LIST OF TABLES

Table Page

1 Measurements for n. sp. 1 ...... 33

2 Measurements for Necronectes drydeni ...... 33

vii ACKNOWLEDGEMENTS

I would like to thank all those who helped, supported and guided me through my master’s program and research. First and foremost I would like to thank my advisor

Rodney Feldmann for guiding me through my thesis research, helping me on a personal level when I first arrived to the United States, supporting me emotionally and answering every question I had. He provided me with knowledge and means for success.

I would like to thank John Nance from Calvert Marine Museum Solomons,

Maryland for providing the fossils. Special thanks goes to my committee members

Carrie Schweitzer and Neil Wells for taking the time to teach me. I would also like to thank the administrative secretary of Geology Department, Kelly Thomasson. My utmost gratitude goes to my mother and wife for supporting me and being part of my journey in the last two years.

viii SUMMARY

A collection of decapod fossils from the Miocene St. Marys Formation, Little

Cove Point Member, was examined. Three different genera were recognized,

Necronectes A. Milne Edwards, 1881, Callinectes Stimpson, 1860, and Cancer Linnaeus,

1758, comprising 6 species. Cancer included 4 species, Cancer irroratus Say, 1817;

Cancer borealis Stimpson, 1859; and two new species. Necronectes is represented by

Necronectes drydeni Rathbun, 1935. Callinectes was also represented by a single species within the collection, Callinectes sapidus Rathbun, 1896. Most of the fossils were small relative to normal adult size. The paleoecology was similar to the present day ecology based on study of recent faunas, lithology, and paleoecology. The paleo-environment was shallow marine within the temperate climate zone.

1 INTRODUCTION

The origin of decapods is still poorly understood. The earliest decapod that has been recorded in the geological record dates back to the Middle Devonian. During that time decapods had lower diversity in fossil assemblages as compared with other arthropod groups as well as pelecypods, brachiopods, and corals. Nevertheless, they remain an important element in studying the paleoecosystem. Decapod fossils in the

Paleozoic are very rare. Only three species have been identified from that era (Schram et al. 1978; Schram, 2009; Feldmann and Schweitzer, 2010; Jones et al., 2014). The diversity of Decapoda increased in the Mesozoic and reached its peak during the

Cenozoic. Around 2000 species have been recognized in Cenozoic rocks (Schweitzer et al., 2010). The earliest true crab fossils, Brachyura, that are known date back to the

Jurassic. The radiation of crabs began during the Cretaceous as Gondwana continued breaking up. This event resulted in crabs occupying and adapting to new, diverse environments. Many researchers have described and published works on decapods. One of the most useful publications on Atlantic coast Cenozoic decapods and their classification and description is that of Rathbun (1935). She described 10 families and more than 50 species from different formations that are located along the Atlantic coast.

Feldmann et al. (1998) described ten species of brachyuran decapods from the Eocene

Castle Hayne Formation of North Carolina. The study of decapod fossils has advanced rapidly in the last 20 years: decapods are a useful tool for paleo-environmental 2 interpretation. Nations (1975) studied the distribution of recent and fossil Cancer. He also reclassified the species into subgenera. Schweitzer and Feldmann (2000) re-evaluated

Cancer and elevated subgenera to generic level. Williams (1984) studied shrimps, lobsters, and crabs of the eastern coastline of the United States. More researchers have contributed to the identification of fossil decapods from the eastern coast of North

America including Rathbun (1929, 1935), Roberts (1955), Blow and Manning (1996),

Bishop and Palmer (2006), Feldmann et al. (1998, 2013, 2018) and Feldmann and

Schweitzer (2016, 2017).

The St. Marys Formation is a well-known Miocene formation on the eastern coast of the United States. It contains more than 600 species of marine organisms, both vertebrate and invertebrate fossils, including diatoms, dinoﬂagellates, foraminiferans, sponges, corals, polychaete worms, abundant and diverse mollusks, ostracods, decapod crustaceans, barnacles, brachiopods, echinoderms, sharks and rays, bony ﬁshes, turtles, crocodiles, pelagic birds, seals, sea cows, odontocetes and mysticetes, isolated and fragmentary remains of large terrestrial mammals, palynomorphs, and land plants (Clark et al., 1904; Gottfried et al., 1994; Eshelman et al., 2007; Godfrey and Barnes, 2008;

Ward and Andrews, 2008). Ward (1992) studied both Bivalvia and Gastropoda and provided a biostratigraphy of the middle Atlantic Coastal Plain.

Decapod faunas have always been of interest for paleontologists, although the St.

Marys Formation decapods have been largely unstudied. One of the earliest contributors to identification of crab fossils from the St. Marys Formation was Mary Jane Rathbun, who described a new species of decapod in 1935, Necronectes drydeni. It was collected from the Little Cove Point Member of the St. Marys Formation. Feldmann and 3 Schweitzer (2016), were able to identify a new species of giant spider crab, Libinia amplissimus, from the Little Cove Point Member. Also Libinia marylandicus Palmer,

1935, was identified in St. Mary Formation (Feldmann et al., 2018). Both Gernant (1971) and Whitmore (1971) have published paleoecological interpretations of Maryland

Miocene formations based on the invertebrate and vertebrate fauna respectively. Ward

(1992) studied the molluscan assemblages of the Miocene strata at Chesapeake Bay and made a paleoecological interpretation. Shideler (1994) studied the stratigraphy of the

Miocene in Calvert Cliffs and made a paleo-environmental interpretation based on the depositional settings. Kidwell et al. (2015) studied Miocene stratigraphy and paleoenvironments of the Calvert Cliffs.

The objectives of this study are to prepare and describe the decapod portunid and cancrid fossils, to identify them systematically, and to reconstruct the paleoenvironment based on the new data that will be obtained from the decapod classification.

4 GEOLOGICAL SETTING

The St. Marys Formation in Maryland is located in the central part of the Atlantic coast. It is exposed in St. Mary’s and Calvert counties of Maryland, along the western shore of Chesapeake Bay. It lies within the upper Miocene stratigraphic sequence. It is also located in the subsurface of the eastern shore of Maryland. The unit was deposited in the Salisbury Embayment (Means, 2010), which extended over approximately 5,000 square miles, and formed during the Cretaceous. At that time, an episode of global warming resulted in sea level rising. The current coastal plain was covered with water which made the continental margin broader than at the present day. Due to tectonic forces on the continental margin, the area subsided and the coastline shifted seaward. Regional reactivation of normal faults resulted in the formation of the Salisbury Embayment.

During the Miocene, 20 to 10 million years ago, the area was subjected to intense uplift which increased the flux of eroded sediments to the basin forming the Chesapeake

Group (Means, 2010). The group has been subdivided into beds to which numbers have been assigned. Beds 20-24 encompass the St. Marys Formation (Ward, 1992). According to the Maryland Geological Survey (Shattuck, 1904), the Chesapeake Group consists of three formations while Ward and Blackwelder (1980) divided the Group into seven formations, represented in ascending order by the Old Church, Calvert, Choptank, St.

Marys, Eastover, Yorktown, and Chowan River formations. The Calvert Formation

5 consists of marl and sandy clay layers. Fossils are present throughout the formation. The maximum water depth in the Chesapeake Group, approximately 40-50 meters, occurred during the deposition of the Calvert Formation. The overlying Choptank Formation consists of fine, yellow quartz sand and blue green sandy clay. The fauna in this formation differs from the underlying Calvert Formation by being shallower. The St.

Marys Formation was deposited in late middle Miocene and early late Miocene. It overlies the Choptank Formation and underlies the Eastover Formation. The St. Marys

Formation represents the transition from an open marine shelf to a tidally inﬂuenced coastal embayment (Clark et al., 1904). It consists of three members, Conoy, Little Cove

Point, and Windmill Point. In the late middle Miocene, the area was subjected to transgression and the Conoy Member was deposited. It consists of clay and sandstone deposited in a shallow inner bay. This event was followed by a brief period of regression and then a greater transgression in which the Little Cove Point Member was deposited

(Ward, 1992). This member consists of three beds. Shattuck (1904) named these beds 21 to 23. Bed 21 consists of sand and clay interbeds. Bed 22 is sandy clay with abundant fossils. Bed 23 is composed of sandy clay with scattered fossils. The Little Cove Point

Member was deposited in a shallow inner bay setting. Ward (1992) noted several mollusk shell beds. This suggests that the area was influenced by short marine pulses which changed the environment to open shelf conditions. The uppermost member in this formation is the late Miocene Windmill Point Member. It consists of highly fossiliferous sandy clay. During that interval the basin shifted southward and a transgression occurred.

The abundance and diversity of fossils suggests open marine shelf conditions.

6 METHODS

The specimens were prepared using Paleotools microjacks for examination and description. Descriptions have been done by using the standard terminology for the carapace and the pleon. Small specimens were examined under the microscope to describe the carapace precisely. Measurements of the fossils were taken and recorded by using a vernier caliper. All measurements are given in millimeters. After the preparation of the fossils they were whitened using ammonium chloride and photographed using a digital camera. The solid ammonium chloride was inserted in a glass tube that is attached to a compressed air line. Then it was heated until it started to release gaseous ammonium chloride. The compressed air pushes the gas out of the glass tube onto the specimen until it is uniformly white.

7 SYSTEMATIC PALEONTOLOGY

Abbreviations: CCM-I, Invertebrate collection of the Calvert County Museum

Order DECAPODA Latreille, 1802

Infraorder BRACHYURA Linnaeus, 1758

Superfamily CANCROIDEA Latreille, 1802

Family CANCRIDAE Latreille, 1802

Genus Cancer Linnaeus, 1758

Cancer new species 1

Figures 1-21

Diagnosis: Ten anterolateral spines, each divided into one large median spine and two small lateral spines. Five or six nodes arranged in arcuate pattern on branchial region.

Description: Small, outline pentagonal, wider than long. Longitudinally inflated, less so transversely. Carapace regions well defined. Front with five spines including inner orbital spines. Inner orbital spine shorter than lateral orbital spines, triangular. Median spine weakly produced, and at lower level than other frontal spines. Lateral spines less projected than median spine but more produced than inner orbital spines. Fronto-orbital margin slightly inclined upward. Orbits with two fissures, one at mid length and one near outer margin. Three suborbital spines, visible when viewed dorsally. Inner suborbital spine longest, triangular, outer suborbital and intra suborbital spines shorter, equal in size.

Anterolateral margin divided into ten spines including outer orbital spine.

8 Outer orbital spine forms first lobe, smallest, triangular. Spines 2 - 10 equal in size, consist of two small spines bordering one large spine, borders between spines continue as subtle closed fissures on carapace. Posterolateral margin slightly concave with one spine, sometime with second obscure spines. Posterior margin rimmed, narrow, bearing fine granules. Mesogastric region elongated, raised. Metagastric region rounded, raised.

Urogastric depressed. Cardiac region diamond shaped, elevated, wider interiorly, narrower posteriorly, with single central node. Entire axial portion elevated. Inflated protogastric region. Hepatic region inclined toward margin, depressed. Mesobranchial region with 5 or 6 swellings, granules on apex of swellings. Cervical groove not very well defined. Surface ornamented with granules, those on elevated region coarser than in other areas. Pterygostome elevated anterolaterally, ornamented with granules, ornamentation more pronounced on elevated part, margin carinate. Sternum very narrow: sternites 1-3 fused, triangular, granular; sternite 4 largest. Sternites 5 and 7 equal in size; sternite 6 longer, pleonal projection on sternites 4-6, projection narrow on sternite 4.

Sternite 8 not visible. Edge of sternites ornamented with granules. Suture line between sternites distinct, pleonal cavity narrow, deep. Sternite 8 directed inward, could be seen in pleonal cavity. Two granules on sternite 5, one on each side, function as pleonal locking mechanism. Pleon partially preserved. Somite 3 widest followed by 4 and 5. Somite 6 longest, suture line very well defined.

Type: The holotype is CMM-I-2126. The paratypes are CMM-I-4310, CMM-I-

4305, CMM-I-4307, CMM-I-3657, CMM-I-4306, CMM-I-3833, CMM-I-2987, CMM-I-

2863, CMM-I-4311, CMM-I-3796, CMM-I-3970, CMM-I-3806, CMM-I-4312, CMM-I-

4308, CMM-I-4309A, CMM-I-4309B, and CMM-I-3954.

9 Measurements: see Table 1.

Occurrence: Miocene Little Cove Point Member of the St. Marys Formation of the Chesapeake Group. Specimens CMM-I-2126, and CMM-I-4305 to CMM-I-4307 from ½ mile of Driftwood Beach, Calvert County, MD. Specimen CMM-I-3954 from

Chesapeake Ranch Estates north of Seahorse Beach, Calvert County, MD. Specimen

CMM-I-2863 from Langley’s Bluff, St. Mary’s County, MD. Specimen CMM-I-3970 from Stratford Hill, Westmoreland County, VA. Specimens CMM-I-4308 to CMM-I-

4312, CMM-I-2987, CMM-I-3657 and CMM-I-3806 from Chesapeake Ranch Club north of Driftwood Beach, Calvert County, MD. Specimens CMM-I-3796 and CMM-I-3833 from Chesapeake Ranch Estates north of Driftwood Beach, Calvert County, MD.

Remarks: The description was made based on 18 specimens. Although most of the specimens are not very well preserved, they are grouped together based on the similarity of the anterolateral spine morphology and the presence of swellings on the branchial region. The specimens conform to Cancer by exhibiting an axially sulcate frontal region, a weakly concave posterolateral margin, carapace regions well developed axially, and orbits directed forward. Schweitzer and Feldmann (2000) have diagnosed

Cancer based on the previous mentioned characters and the presence of nine anterolateral spines, although they have placed several species with spines that range from 7 – 10 within the genus. The specimen differs from all the species within Cancer by exhibiting

10 anterolateral spines divided into one large median spine and two small lateral spines; therefore, it represent a new species. All specimens are small in size except for one which is relatively larger than the others. All the specimens are molts. The mode of preservation

10 is constant among the specimens, with four fossils showing the preservation of the endocuticle, and exocuticle. Eleven fossils have only the endocuticle preserved.

Cancer borealis Stimpson, 1859

Figure 47

Cancer irroratus Say (part, ♀), 1817: 60. Gould 1841: 322.

Platycarcinus irroratus Gibbes, 1850: 176.

Cancer borealis Stimpson, 1859: 50. R. Rathbun 1884: 769, pl. 260, figs. 4-6; Sumner, Osburn, and Cole 1913: 672; Hay and Shore 1918: 434, pl 35, fig. 2; Rathbun 1930a: 182 text fig. 30; Williams

1965: 175, fig. 156; Power 1977: 71; Schweitzer and Feldmann 2000: 249.

Cancer (Metacarcinus) borealis Nations, 1975: 45, figs. 4, 38-2, 38-3. Williams 1984: 351, text fig. 287.

Modern description: “Antero-lateral margins more broadly rounded; surface much rougher with coarse uneven granules; carapace higher, the convexity ending rather steeply at the dentate rim; lateral spines with denticulate edges; behind the two posterolateral spines there are in old specimens one or two more smaller spines indicated by slight notches. Chelipeds heavier and rougher; hand high, 7 coarsely granulate carinae on outer-upper surface, the uppermost one denticulate; movable finger with a very rough upper margin; ambulatory legs correspondingly rough, side margins of 5th-6th abdominal segments in male more nearly parallel than in irroratus” (Rathbun 1930: 182).

Diagnosis: Nine anterolateral spines including outer orbital spine. Spines have denticulate edges. Carapace rough with irregular granules.

Description of material: Large, outline pentagonal, wider than long.

Longitudinally inflated, less so transversely. Carapace regions well defined. Front 13% of total width with five spines including inner orbital spines, slightly produced with median 11 spine depressed. Front axially sulcate. Lateral spines on front eroded but traces of them remain, larger than inner orbital spines. Fronto-orbital 27% of total width with two fissures on orbits. Anterolateral margin with nine denticulate spines. First spine forms outer orbital, not as wide as second spine. Spines one, eight, and nine triangular. Spines

2-7 quadrate. Notches between spines continue as fissures onto carapace. Posterolateral margin slightly concave, carinate with two distinct spines and one obscure spine. First posterior spine larger. Second spine smaller. Posterior margin rimmed, 35% of total width. Carapace regions well defined. Metagastric region, urogastric region, and pentagonal cardiac regions raised; together they form elevated axial portion. Inflated protogastric region. Hepatic region inclined steeply toward margin. Mesobranchial region with three raised tubercles, cervical groove very distinct axially and indistinct laterally. Surface ornamented with granules, clustered around axial region, decrease in number laterally toward margins. Pterygostome smooth. Sternum narrow, sternites 1 to 3 fused, triangular, 10% of total width. Sternite 4 largest, 20% of total width. Sternites 5,

6, and 7 smaller than 4, separated by suture lines. Sternite 8 not visible. Third maxilliped preserved, 34% of total length, 10% of total width. Merus smooth, smaller than ischium.

Exognath (exopod) longer than ischium, extends to merus. Male pleon narrow, triangular, widening proximally. Telson triangular, smallest segment with pointed end.

Material examined: CMM-I-2796.

Measurements: length, 60.5 mm; width, 97.1 mm; fronto-orbital width, 26.9 mm; frontal width, 13.3 mm; mesogastric width, 14 mm; cardiac region width, 16.9 mm; posterior width, 34.1 mm.

12 Occurrence: Miocene Little Cove Point Member of the St. Marys Formation of the Chesapeake Group; located ⅓ mile from Driftwood Beach Chesapeake Club, Calvert

County, MD.

Remarks: The specimen is a male and a molt with exocuticle partially preserved and endocuticle preserved. The left anterolateral margin is eroded except for spines nine and eight. Only one posterolateral spine is preserved on the left side. Cancer irroratus is similar to C. borealis in having the same number of spines, the division and definition of the regions, and the presence of posterolateral spines, but the edges of the anterolateral spines are not denticulate on C. irroratus. It differs from other species within the genus in several aspects. Cancer bellianus Johnson, 1861, has an anterolateral margin that is divided into ten lobes. Cancer fissus Rathbun, 1908, has eight anterolateral spines that are irregular in size. Cancer fujinaensis Sakumoto, Karasawa & Takayasu, 1992, is vaulted in the hepatic region and has a flat cardiac region. Cancer johngarthi Carvacho, 1989, has a projecting front with the margins cut into nine anterolateral spines with no denticulation. Cancer pagurus Linnaeus, 1758, has ten spines on the anterolateral margin while the anterolateral margins of C. parvidens Collins & Fraaye, 1991, is cut into seven lobes. Cancer porteri Rathbun, 1930, has depressed cardiac and metagastric regions, and a wide first anterolateral spine. The first anterolateral spine of C. plebejus Poeppig, 1836, is very narrow, and the species has a smooth carapace. The front of C. productus Randall,

1839, is markedly produced beyond orbits, and it has ten anterolateral spines.

Cancer irroratus Say, 1817

Figure 48

13 Cancer irroratus Say (part, ♂), 1817: 59, fig. 2. Stimpson 1859: 50; Smith 1873: 546; R. Rathbun

1884: 766, pl 260, figs. 1-3; Sumner, Osburn, and Cole 1913: 671; Hay and Shore 19118: 435, pl. 35, fig.

1; Rathbun 1930a: 180 text fig. 29; Schweitzer and Feldmann 2000: 249.

Platycarcinus irroratus Milne Edwards, 1834: 414.

Cancer sayi Gould, 1841: 323.

Platycarcinus sayi Dekay, 1844: 7.

Cancer borealis Packard, 1867: 303.

Cancer amoenus Connolly, 1923: 337 text figs. 1 and 2, pls. 1-4.

Cancer (Cancer) irroratus Nations, 1975: 45, figs. 4, 42-3, 42-4, not 37-3, 37-4. Williams, 1984:

353, text fig. 288.

Modern description: “Carapace convex, uneven, finely granulate. Antero-lateral spines 9, the first one broad and in part produced to form the orbital spine; spines shallow, edge granulate, the notches between them continued on the carapace as short, closed fissures giving a pentagonal aspect to the spines. Postero-lateral margins raised, granulate carina furnished with two spines, the one nearest the lateral angle small, the other obscure. The median spine of the front is the most advanced and depressed.

Chelipeds shorter than first pair of legs, granulate; upper margin of merus ending in a short, subdistal spine; carpus with granulated ridges and a sharp pyramidal inner spine; manus with 6 longitudinal costae, the two lower ones continued on the finger, the upper one cristate. Legs rather long, compressed; merus of first and second pairs extending well beyond carapace. Side margins of 5th-6th abdominal segment in male converging distally” (Rathbun 1930: 180).

Diagnosis: Nine anterolateral spines including outer orbital spines and two posterolateral spines, last one obscured.

14 Description of material: Medium size, pentagonal, wider than long. Weakly inflated longitudinally. Carapace regions defined medially, lateral regions less so. Front

17% of total width, with five spines including inner orbital spines, slightly produced.

Median spine extends beyond lateral spines. Front axially sulcate. Fronto-orbital width

37% of total width measured about midlength. Orbits with two deep, well defined, open fissures. Anterolateral margin with nine spines. First spine forms outer orbital corner, wider than second spine. Ninth spine widest. Spines quadrate; notches between spines continue as fissures onto carapace, distal margins of spines smooth. Posterolateral margins concave, carinate, with two spines. First spine distinct, posterior to anterolateral angle. Directed anterolaterally. Second spine obscure. Posterior margin rimmed, 41% of total width. Carapace regions moderately defined medially. Mesogastric and metagastric regions slightly elevated. Metagastric region with triangular array of about six tiny granules. Cardiac region pentagonal, elevated, with two nodes at midlength. Urogastric region marked by depression between mesogastric and cardiac regions. Protogastric regions slightly inflated. Hepatic regions depressed. Mesobranchial regions with three raised tubercles. Cervical groove distinct axially and indistinct laterally. Surface ornamented with granules, clustered in posterior portion of carapace.

Material examined: CMM-I-2616.

Measurements: width, 41.2 mm; length, 30.4 mm; fronto-orbital width, 15.4 mm; frontal width, 7 mm; cardiac region width, 6.1 mm; posterior width, 16.9 mm.

Occurrence: Miocene Little Cove Point Member of the St. Marys Formation of the Chesapeake Group, Westmoreland State Park, Westmoreland County, VA.

15 Remarks: Only the dorsal surface of the specimen is preserved. The left anterolateral margin is eroded. The distal termination of the rostrum is not preserved. The mesobranchial region is marked by the presence of two rows of pits in the axial part that are concave to the proximal part of the mesobranchial region. Cancer irroratus is similar to C. borealis in having the same number of spines, the division and definition of the regions, and the presence of posterolateral spines, but C. irroratus has no denticulation on the anterolateral spines. Cancer bellianus, C. pagurus, and C. productus differ from C. irroratus by exhibiting ten anterolateral spines. Cancer fissus has eight spines on the anterolateral margins, while C. parvidens has seven spines. Cancer fujnaensis has a vaulted hepatic region and a flat cardiac region. Cancer johngarthi differs from C. irroratus by having a projected front. The carapace of C. plebejus is smooth. The cardiac and metagastric regions in C. porteri are depressed, and it has a wide first anterolateral spine. The specimen is a molt with the only the endocuticle preserved.

Cancer new species 2

Figures 49, 50

Diagnosis: Nine anterolateral spines, triangular, with several small terminal spines.

Description of material: Carapace large, wider than long, well defined carapace regions, longitudinally inflated, less so transversely. Fronto-orbital margin broken.

Anterolateral margin with 9 spines including outer orbital spine, spines triangular, inclined upward. Tip of spines bears large central spine and small lateral spines. Lateral spines increase in size distally from main spine. Border between spines narrow, does not continue onto carapace. Posterior margin short, 29.6% of total width, granulated.

16 Mesogastric region inflated, joined with elongated, raised metagastric region. Urogastric region and cardiac region broken. Axial portion of carapace elevated. Protogastric region rounded, inflated. Hepatic region depressed slightly. Mesobranchial region with three faintly raised tubercles. Cervical groove distinct axially and indistinct laterally. Surface ornamented with granules, ornamentation clustered axially, decreasing in density laterally. Granules more pronounced laterally, smaller axially. Sternum narrow, partially preserved. Pleon long and wide. Somite three widest, 20.3% of total width. Somite four

16.9% of total width. Somite five and six fused, longest, partially preserved, 16.1% of total width. Somites 3-6 decrease in width and increase in length distally. Somites ornamented with fine granules.

Merus of pereiopod 1 partially exposed, upper surface with small spines. Distal part articulates with carpus and terminates with three large spines. Carpus 27.1% of total carapace width. Surface ornamented with four carinae, upper carina with numerous spines directed distally, at mid point it diverge into two ridges with spines; at distal articulation, two ridges connected by row of small spines. First ridge terminates with large spine at distal end. Second ridge terminates with small spine at distal end. Second carina short, terminates slightly before third carina with a few small spines, directed distally. Third carina terminates around midpoint of carpus with a few small spines directed distally. Second and third carinae located on outer surface, with spines increasing in size distally. Fourth carina on lower surface of carpus, concave in shape, spines larger distally, smaller proximally, directed distally. Distal lower part of carpus raised. Inner surface smooth, granulated. Cheliped becoming higher distally, with seven ridges. Upper surface with two ridges, outer surface with four ridges, lower surface with

17 one ridge. Ridges spinulated, spines more pronounced on upper and upper outer surface and diminishing in size on lower outer and lower surface. Spines alternate in size, directed distally. Third ridge with fewer spines than first, second, and fourth ridges.

Distal margin with broad, smooth rim. Movable finger 27.1% of total carapace width, with five cutting spines, first and second proximal spines small, third spine largest, domal shaped. Fourth and fifth spines decrease in size, domal-shaped. Upper surface with three spinose ridges. Spines larger proximally, decrease in size distally. Outer surface smooth.

Fixed finger 24.5% of total width, with four domal-shaped spines. First proximal spine largest, second and third spines elongated, fourth spine smallest. Two ridges extend from cheliped on outer surface, ridges with fine serrated spines.

Type: Holotype is CMM-I-4014.

Measurements: Posterior margin width, 35 mm; carpus, 31.9 mm; movable finger,

32 mm; fixed finger, 29 mm; cheliped, 58 mm; pleonal somite three, 24 mm; pleonal somite four, 20 mm; pleonal somites five and six, 19 mm.

Occurrence: Miocene bed 23 of the Little Cove Point Member of the St. Marys

Formation of the Chesapeake Group, Windmill Point, St. Mary’s County, MD

Remarks: The specimen is a male with endocuticle preserved. The entire anterolateral margin is eroded except for two spines. The number of spines is based on the presence of fissures. The fronto-orbital margin is eroded and the posterolateral margin is not preserved. The ventral side of the carapace has been detached and displaced from the dorsal side. The sternum is covered with sediments, any attempt to remove the sediment resulted in destroying the preserved cuticle. There is not enough evidence to determine if the fossil was a molt or a corpse. There are barnacle epibionts attached to the

18 left side of the carapace. The barnacles are clustered in the proximal epibranchial region.

Their presence indicates that the range of motion of the pereiopod is insufficient for grooming (Tashman et al., 2018). The lack of the frontal margin and posterolateral margin made it difficult to place within a genus. It was placed in Cancer based on the similarity of its carapace with Cancer borealis, although it differs from C. borealis by having small spines on the anterolateral spines. Also, C. borealis has a longer movable finger than fixed finger and lacks any spines on the cheliped. Cancer irroratus differs from the specimen by lacking any spines on the cheliped and exhibiting more cutting spines on the movable and fixed finger. Cancer productus has no spines on the propodus.

Cancer plebejus has a similar cheliped to the specimen but it differs in having 6 carinae on the palm and more sharp cutting spines. Cancer porteri has more cutting spines and no spines on the cheliped. Cancer bellianus has ten anterolateral spines and the cheliped bears minute spines on the upper part. Cancer fissus has eight spines on the anterolateral margin. Cancer pagurus has smooth chelipeds with no spines or ridges. Cancer parvidens has seven anterolateral spines and smooth chelipeds. Cancer fujinaensis has a vaulted hepatic region. Cancer johngarthi has four carinae on the outer face of the chelipeds.

Family PORTUNIDAE Rafinesque, 1815

Subfamily NECRONECTINAE Glaessner, 1928

Genus Necronectes A. Milne Edwards, 1881

Necronectes drydeni Rathbun, 1935

Figures 22-46

19 Necronectes drydeni Rathbun, 1935: 107. Tice, 1962: 1127; Martinez-Ortiz, Alvarado-Ortega, and Cuevas-Garcia, 2017:12.

Diagnosis: Eight anterolateral spines including outer orbital spine. Median groove in sternite four in front of pleon.

Modern description: “A single specimen showing the carapace and the ventral surface of the body and the right arm. Carapace nearly half again as long, slightly convex in the middle portion, lateral rim depressed especially at the hepatic region. Surface smooth, punctate, carapace badly crushed in the gastric and frontal regions; edge of front destroyed, a furrow leads backward from either side of the mid-orbital spine. Lateral spines low, broader than long, except perhaps the seventh and the eighth; the latter is narrower at base than the seventh; the first spine is small and triangular, the second to the sixth inclusive are more or less lobiform, and blunt pointed. The comparative width of the spines is as follows: No. 1 narrowest, 2 and 8, 3 and 4, 5 and 6, 7 widest. Ischium of outer maxillipeds with raised inner portion which is one third of the width of the article and is set off by deep groove. The abdomen is somewhat wider than in the male of N. proavitus but probably is that of a male, as segment 4 and 5 at least are fused. The telson is longer in proportion to its width than in proavitus. There is deep median groove in the sternum in front of the abdomen; there is no impressed lone on the sternum between the maxillipeds, as in proavitus and vaughni. The right arm is stout, posteriorly curved, and extends laterally a little beyond the carapace” (Rathbun, 1935: 107).

Description of material: Carapace small, outline ovate, width greater than length, regions moderately defined. Front not very well preserved in all specimens. Front axially sulcate with three spines. Outermost spines form inner orbital spines, and one spine in the

20 middle. Orbits with no fissures, circular. Anterolateral margins with eight spines. First spine forms outer orbital, narrowest, seventh spine widest followed by spine eight. Spines two to six increase in width. Spines triangular, directed forward, tips of spines acute.

Posterolateral margin rimmed, weakly concave. Posterior margin narrow, smooth.

Carapace moderately vaulted longitudinally, weakly vaulted transversely. Carapace regions moderately defined. Metagastric and mesogastric regions fused, and inflated, urogastric region narrow marked by depression. Cardiac region slightly raised, shape appears to be rectangular with three nodes. Two nodes on anterior part, one node on posterior part forming triangle. Protogastric region elevated. Hepatic region depressed.

Epibranchial region smooth. Mesobranchial and metabranchial regions fused, and inflated, inflation extends from spine eight as ridge. Cervical groove distinct axially and indistinct laterally, surface smooth, punctate. Pterygostome smooth. Sternum wide, oval.

Sternite 1-3 fused, diamond shaped, fused to sternite four. Sternite 4 largest, with transverse median groove, sternites 5-7 decrease in width, sternite 8 smallest, and visible.

Suture lines between sternites 4, 5, 6, and 7 well defined. Merus of third maxillipeds smooth, exognath longer than ischium, extends to merus. Pleon narrow. Pleonal cavity reaches mid-point of sternite 4. Merus of first pereiopod extends beyond carapace, smooth, not ornamented. Width 60% of length (based on one specimen CMM-I-4315).

Coxa small, smooth. Basis triangular, shorter than ischium.

Material examined: CMM-I-3996, CMM-I-3931, CMM-I-2941, CMM-I-4043,

CMM-I-4316, CMM-I-3920, CMM-I-4314, CMM-I-4319, CMM-I-4320, CMM-I-4318,

CMM-I-4313, CMM-I-4317, CMM-I-231 and CMM-I-4315.

Measurements: see Table 2.

21 Occurrence: Miocene Little Cove Point Member of the St. Marys Formation of the Chesapeake Group. Specimens CMM-I- 4313 to CMM-I-4320 from Chesapeake

Ranch Club north of Driftwood Beach, Calvert County, MD. Specimens CMM-I-3920,

CMM-I-3996 CMM-I-3931 and CMM-I-2941 from Driftwood Beach, Calvert County,

MD. Specimen CMM-I-231 from Chesapeake Ranch Club, Calvert County, MD.

Specimen CMM-I-4043 from Chesapeake Ranch Estates north of Driftwood Beach,

Calvert County, MD.

Remarks: The description was made based on 14 specimens. The orbits and front of most of the specimens were not very well preserved. The anterolateral margin of 12 specimens was not preserved. The specimens were grouped together based on similarity in carapace regions and the sternum. They all were classified as N. drydeni based on the presence of 8 anterolateral spines and a medial groove on sternite 4. Necronectes includes eleven species, each with its own distinct traits. Necronectes vidalianus A. Milne-

Edwards, 1881b, has wider than long anterolateral spines and they are closely spaced.

Necronectes nodosa Schweitzer et al., 2002, has scattered lumps or rounded nodes on the branchial region (Schweitzer et al., 2002). Necronectes summus Collins and Donovan,

1995, is only known for its chelae, which are not preserved in the new specimens.

Necronectes collinsi Schweitzer et al., 2006, presents an epibranchial ridge extending axially from the eighth spine transversely to the cardiac region (Schweitzer et al., 2000).

Necronectes tajinensis Vega et al., 1999, has two unique traits; the outer orbital spine is peculiarly very thin and curved, and in addition to that, all its anterolateral spines have convex edges (Vega et al., 1999). Necronectes batalleri Via, 1932, is more vaulted than the other species (Via, 1941). In Necronectes schafferi Glaessner, 1928, the anterolateral 22 spines are of irregular size, the three in the central position are the largest, the ones in the front and back are progressively smaller (Glaessner, 1928). Necronectes drydeni differs from N. proavitus Rathbun, 1918, by lacking a ptergostomal region with granules.

Moreover the carapace regions on N. proavitus are much more distinct than on N. drydeni. Necronectes beaumonti A. Milne-Edwards, 1864, lacks any ornamentation on the carapace and the anterolateral spines increase in size from 1-8. It differs from N. vicksburgensis Stenzel, 1935, by lacking three subparallel prominences on the branchial region (Rathbun, 1935).

The original description was made by Rathbun (1935) for a specimen where the anterolateral margins were eroded a little, so it lost the curving forward feature of the anterolateral spines. All the specimens are small in size with only the endocuticle preserved except for one specimen that shows the exocuticle. All the specimens are molts.

Genus Callinectes Stimpson, 1860

Callinectes sapidus Rathbun 1896a

Figures 51-54

Lupa hastata Say, 1817: 65.

Portunus diacantha Latreille, 1825: 190.

Lupea dicantha Milne Edwards, 1834: 451.

Lupa dicantha Gould, 1841: 324, pl. 6; De Kay 1844: 10, pl. 3, fig. 3

Callinectes hastatus Ordway, 1863: 568; A. Milne Edwards 1879: 224; R. Rathbun 1884: 775, pl.

267.

Callinectes sapidus Rathbun, 1896a: 352, pls. 12, 24, fig. 1; Hay and Shore 1918: 432, pl. 35, fig.

1; Fowler 1912: 416, pls. 128-130; Piers 1923: 83; Rathbun 1930a: 99, pl. 47; Williams 1974b: 778, figs.

23 1, 16, 17, 19d, 21,23b-c; Felder 1973: 55, pl. 8, fig. 7; Powers 1977: 78; Williams 1984: 376, figs. 293g,

299.

Modern description: “Carapace of adult male from 2⅙ to 2½ times as broad as long, moderately convex; granules of medium size, crowded on the cardiac and inner branchial regions, scattered and faintly marked on the anterior half of the carapace.

Length of intramedial region about one-half or a little less than one-half its anterior width. Frontal spines two, broadly triangular, subacute, extremities almost rectangular; faint indications of a median pair of denticles on their oblique inner margins sometimes present; median subfrontal spine conical and strong. Inner supraorbital spine broad, faintly bidentate, less advanced than the front; of the superior fissures the outer is shorter than the inner, both are closed except at anterior extremity where there is a shallow V- shaped opening; outer spine elongate triangular, acute; inner suborbital spine acute.

Lateral spines 2 to 8 acuminate, concave on both margins; lateral spine in males from two to about four times the length of preceding spine. Costae of wrist and hand marked with depressed granules, often almost smooth to the eye; lower costa obsolete on greater part of palm. Penultimate segment of male abdomen much constricted in its proximal half, widening at both extremities; terminal segment elongate, obtuse, lateral margins convex proximally, slightly concave or straight distally; appendages of first segment reaching nearly to or beyond the extremity of the abdomen, approximate for their basal half, with only a slight outward curve, distal portions widely divergent except at tips. Abdomen of adult female very broad, margins of third, fourth, and fifth segments separately convex; terminal segment longer than wide” (Rathbun 1930: 99).

24 Description of material: Carapace broad, width greater than length. Weakly convex longitudinally and transversely. Carapace regions not well defined. Anterolateral margin convex, longer than posterolateral margin. Last anterolateral spine longer than preceeding spines. Posterolateral margin strongly concave, rimmed. Mesogastric and metagastric regions fused. Urogastric region marked by depression. Cardiac region raised. Protogastric region slightly elevated. Hepatic region depressed. Epibranchial, mesobranchial, and metabranchial regions fused and inflated. Last anterolateral spines continue onto branchial region as elevated ridge. Cervical groove distinct axially and indistinct laterally. Surface smooth. Sternum wide, oval. Sternites 1-3 fused, sternite 4 largest, with transverse median ridge followed be groove, sternites 5-7 decrease in size.

Sternite 8 well defined. Immature female pleon reaches groove line on sternite 4, triangular. Telson small, narrow. Posterior to telson, two fused segments. Division of fused somites not clear. Female telson reaches posterior part of sternite 4. Pleon oval, wider than immature female pleon. Telson wider than immature female telson, semi- circular. Posterior to telson pleon divided into 3 segments that decrease in size.

Material examined: CMM-I-3906 and CMM-I-3688.

Measurements: For specimen CMM-I-3906, width, 104.03 mm; length, 61.3 mm; fronto-orbital width, 41.85 mm; frontal width, 19.49 mm.

Occurrence: Miocene Little Cove Point Member of the St. Marys Formation of the Chesapeake Group, Driftwood Beach, Calvert County, MD.

Remarks: The specimens are not well preserved. The entire anterolateral margin has been eroded. There is not enough evidence to judge if these specimens were corpses or molts. Some fossils show the endocuticle and the exocuticle preserved, while other

25 fossils show only the endocuticle preserved. The carapace has a hole where the protogastric and mesogastric regions are located. The identification of the specimen was made based on the observation and description of the sternites and pleon. Callinectes possesses a T shaped male pleon, whereas the female has an oval pleon. The specimens conform to the genus Callinectes, because they exhibit a long last anterolateral spine, and an oval female pleon. The exact species identification is not definite and was based on the similarity between the specimens and a specimen of Callinectes sapidus illustrated by

Warner (1994). Both specimens have the female pleon reaching little behind groove of sternite 4. The width of somites seems similar. One of the specimens represents an immature female pleon which might be mistaken for a Portunus male pleon. The first somite in Portunus does not extend very much, and sternite 8 is almost completely visible, while in immature Callinectes sapidus the first somite is wider and sternite 8 is partially visible.

26 DISCUSSION

Paleoecological interpretation for the Miocene crab fossils is based on studying the recent ecology of Cancer irroratus, Cancer borealis, and Callinectes sapidus.

Literature pertaining to ecological interpretations based on other fauna in the St. Marys

Formation, and the depositional environments based on lithology of the formation is also used.

Recent ecology

Brachyurans have been found to inhabit a variety of environments. They can live in fresh water, on land, and in the sea. Marine crabs live in numerous habitats from the ocean floor at 6000 m depth to intertidal shores. The genus Cancer is distributed in the temperate zone. There are no known occurrences of Cancer where the mean surface water temperature is less than 4.4O C (Mackay, 1943). In some cases, some Cancer species can occur in subtropical water, but it is usually in deeper water where there are cold currents that lower the water temperature. Mackay (1943) recorded the presence of

Cancer borealis, south of Dry Tortugas, Florida.

Cancer borealis is usually found on rocky bottoms in water depths between 20 and 400 m. It is most abundant in 150-400 m water depth. The shallower depths are usually inhabited by juvenile members of the species, whereas the deeper part is occupied by larger, more mature adults. The optimum temperature for Cancer borealis survival is

8 to 13O C (Williams, 1984). Recent studies of the species indicate that mature males and 27 females migrate to shallower depths to mate; the juvenile stages prefer the shallow water to avoid predation. The males and females of the species have different molting periods.

Large females molt in December, while large males molt from January to March. Males between 40 and 60 mm molt in May (Williams, 1984). The species usually shares its habitat with Homarus americanus (Jeffries, 1966).

Cancer irroratus lives on sandy and rocky bottoms depending on its size.

Younger and smaller members of the species usually occupy sandy bottoms, while older and larger members occupy rocky bottoms. Cancer irroratus lives on the continental shelf in water depths between 18-390 m. The highest population density of the species is found between 40-60 m. The optimum water temperature for the species’ survival is between 6O and 9.9O C (Musick and McEachren, 1972).

Cancer irroratus individuals feed on small sea urchins, the bivalve Modiolus modiolus, and ectoprocts. They also feed on Polychaeta. It would not be surprising to assume a similar diet for fossil C. irroratus. Haefner and Engel (1975) studied the species in the Chesapeake Bay, and found that adults usually migrate from deeper offshore sites to the shallow bay from late fall to early spring. All of the C. irroratus found in the bay were paper shell crabs. Adults usually migrate there to molt where cold bottom water would enhance the chances for survival. The molting process of the males usually starts around late December and late January while females molt in early December. The molting process usually occurs when the salinity is around 20‰ and the temperature is 7O

C. The size and sex of the crab is also a factor in determining the time of the molting.

Males and females greater than 60 mm molt during January-March, November-December

28 respectively. Males between 21-33 mm molt between May and July (Reilly and Saila,

1978).

Cancer irroratus and Cancer borealis, can be found occupying the same environment, the former is usually found on sandy bottoms, while the latter is found on rocky bottoms. The heavier and stronger claws of C. borealis helps the animal in digging in coarse gravel and boulder bottoms for protection and food. The light claws of C. irroratus give it an advantage for faster disappearance in sandy bottoms. Both species live in cool, deep water where the average temperature is 6.8O to 14.4O C. During mating both species travel to shallow parts of the shelf to reproduce. Juvenile crabs remain there to avoid predation. In some cases, young, small C. irroratus can travel into the estuaries during fall, winter, and spring (Williams, 1984).

Callinectes sapidus, the blue crab, is usually found along the coastline. It can inhabit the bottom of fresh water estuaries, and shallow open marine environments. It is usually distributed in water depths up to 90 m, but the highest density is found in 35 m water depth. The blue crab lays its egg in the estuaries and very shallow ocean. The larvae develop in the ocean and migrate back to the estuaries as young crabs to develop to adult mature crabs. The blue crab can tolerate temperature that ranges from 3O to 35O C

(Williams, 1984).

Paleoecology

According to Gernant (1971), the entire St. Marys Formation is of a shallow marine origin. His conclusion was based on studying the invertebrate macrofossil fauna preserved in the formation. The presence of the bivalves Lyropecten and Ensis in unit 21 indicates a very shallow subtidal area. Unit 22 has a diverse assemblages of macrofossils

29 that include the gastropods Turritella, Nassarius, Mangelia, Lunatia (now known as

Euspira), and the bivalves Spisula and Mercenaria. These taxa indicate that the paleo- environment was shallow marginal marine. The presence of great numbers of Nassarius and Mangelia indicate the depth was most likely less than 30 m. Unit 23 has a similar fossil assemblages to unit 22, so the paleo-environment was of similar depth. Whitmore,

Jr. (1971) studied the vertebrate fauna in the Chesapeake Group. The group yields numerous fossils like Cetacea, Sirenia, crocodiles, turtles, fishes, birds, and plants. Based on the fauna and flora he estimated the average paleotemperature was 19.4O C with highest temperatures of 23.8 O C. The area was most likely within the temperate climate zone.

Ward (1992) studied the molluscan assemblages of the St. Marys Formation. He concluded that it was deposited in a shallow lagoonal environment with normal salinity.

He suggested that the Little Cove Point Member reflects an inner bay condition.

Depositional environment

Shideler (1994) studied the lithology of the St. Marys Formation and made an interpretation of the paleo-environment based on the sediments and structures. He observed that zone 20 consists of argillaceous deposits, and that it lacks any structure that would occur from sediment movement on the seafloor. This indicated that suspension was the main transport mechanism. There was no bioturbation observed. Also, the unit has a low carbonate content. He suggested that zone 20 was deposited in a muddy prodelta. Zone 21 has a similar setting to zone 20 except that zone 21 has a higher sand ratio, which means closer proximity to the source area and a higher energy level than zone 20. Zone 21 was deposited on a sandy delta front. Zone 22 represents a beach

30 environment. It is composed entirely of sandy units. Also, it has large scale cross stratification which indicates an increase in the wave and current energy over that of the previous units. Lithological observation of unit 23 suggests a lower energy level than zone 22, with the presence of bioturbation. He concluded the paleo-environment was a lower deltaic plain. During the deposition of the St. Marys Formation, the area was subjected to regression, which led to a shallowing-upward sequence.

Based on the observations of the recent ecology of Cancer irroratus, Cancer borealis, and Callinectes sapidus, and employing the data presented by Whitmore, Jr

(1971), Gernant (1971), Ward (1992) and Shideler (1994), the paleoecology can be inferred from present day ecological studies. The environment was shallow marine, less than 30 m depth. The locality was within the temperate zone where temperatures did not exceed 23.8O C. The two new Cancer species and Necronectes drydeni lived in conditions similar to these of Cancer irroratus and Cancer borealis. They most likely lived on deeper parts of the shelf where depth did not exceed 400 m, and migrated back to shallow water to mate. The juvenile members of the species lived in shallow water where depth did not exceed 30 m. This is evident from the small size of the fossils.

Juveniles preferred cold water where the average water temperature was between 4.4O to

6O C.

31 CONCLUSIONS

During the deposition of the Little Cove Point Member of the St. Marys

Formation, the ecology was shallow marine with about 30 m water depth. The climate was within the temperate zone where the mean surface water temperature was between

4.4O-9.9O C, and the mean atmospheric temperature did not exceed 23.8O C. The small size of the fossils indicates that they were juvenile and preferred shallow water to have a better chance of surviving. The two new species of Cancer lived in environmental settings similar to these of Cancer irroratus and Cancer borealis.

32 APPENDIX

Table 1. Measurements in mm for n. sp. 1.

cataloge # Width length fronto-orbital (FO) front (F) posterior width (PW) FO/W F/W PW/W CMM-I-2126 33 21.5 12 6 0.363636 0.181818 CMM-I-4305 21 16 8.5 5.5 6 0.404762 0.261905 0.285714 CMM-I-4306 21.9 CMM-I-4307 23 CMM-I-3833 33.7 21.5 11.2 5.2 6.8 0.332344 0.154303 0.20178 CMM-I-3970 40.5 26.7 14 7.8 9.5 0.345679 0.192593 0.234568 CMM-I-4310 40.2 26.2 13.8 7 0.343284 0.174129 CMM-I-4311 29.2 19.8 12.3 6.6 6.7 0.421233 0.226027 0.229452 CMM-I-4312 30.1 20.4 10.9 4.2 0.362126 0.139535 CMM-I-3796 82.8 CMM-I-3954 CMM-I-3806 50.9 CMM-I-3657 CMM-I-2863 42.1 27.1 10.4 0.247031 CMM-I-2987 31.6 20 11.6 4.4 7.3 0.367089 0.139241 0.231013 CMM-I-4308 CMM-I-4309A 27 CMM-I-4309B 25.2 16.6 10 4.5 4.5 0.396825 0.178571 0.178571 Table 2. Measurements in mm for Necronectes drydeni.

cataloge # Width length fronto-orbital (FO) front (F) posterior width (PW) FO/W F/W PW/W CMM-I-3931 40.6 27.3 12.2 5.6 0.300493 0.137931 0 CMM-I-231 30.7 23.2 14 6.5 0.456026 0.211726 0 CMM-I-3996 26.1 17.7 11.2 5.4 5.3 0.429119 0.206897 0.203065 CMM-I-3797 CMM-I-4043 41.3 25.6 CMM-I-3920 42.1 27.3 CMM-I-4320 39.6 26.1 CMM-I-4319 29.4 19.8 13.3 6.2 9.6 0.452381 0.210884 0.326531 CMM-I-2941 43.5 CMM-I-4316 31.6 21.7 12.3 6.2 9.6 0.389241 0.196203 0.303797 CMM-I-4314 50 33.7 CMM-I-4313 33 23.5 CMM-I-4318 27.5 21.5 CMM-I-4317 34.8 25 14.9 7.3 0.428161 0.20977

Figure 1. n. sp. 1, dorsal view, CMM-I-2126. Scale bar = 1 cm.

Figure 2. n. sp. 1, dorsal view, CMM-I-4310. Scale bar = 1 cm.

Figure 3. n. sp. 1, ventral view, CMM-I-4310. Scale bar = 1 cm.

Figure 4. n. sp. 1, dorsal view, CMM-I-4305. Scale bar = 1 cm.

Figure 5. n. sp. 1, dorsal view, CMM-I-2987. Scale bar = 1 cm.

Figure 6. n. sp. 1, dorsal view, CMM-I-3833. Scale bar = 1 cm.

35 Figure 7. n. sp. 1, dorsal view, CMM-I-4306. Scale bar = 1 cm.

Figure 8. n. sp. 1, dorsal view, CMM-I-3657. Scale bar = 1 cm.

Figure 9. n. sp. 1, dorsal view, CMM-I-4307. Scale bar = 1 cm.

Figure 10. n. sp. 1, ventral view, CMM-I-4307. Scale bar = 1 cm.

Figure 11. n. sp. 1, dorsal view, CMM-I-3806. Scale bar = 1 cm.

Figure 12. n. sp. 1, dorsal view, CMM-I-3970. Scale bar = 1 cm.

37 Figure 13. n. sp. 1, dorsal view, CMM-I-3796. Scale bar = 1 cm.

Figure 14. n. sp. 1, dorsal view, CMM-I-4311. Scale bar = 1 cm.

Figure 15. n. sp. 1, dorsal view, CMM-I-2863. Scale bar = 1 cm.

38 Figure 16. n. sp. 1, dorsal view, CMM-I-3954. Scale bar = 1 cm.

Figure 17. n. sp. 1, ventral view, CMM-I-3954. Scale bar = 1 cm.

Figure 18. n. sp. 1, dorsal view, CMM-I-4309B. Scale bar = 1 cm.

39 Figure 19. n. sp. 1, dorsal view, CMM-I-4309A. Scale bar = 1 cm.

Figure 20. n. sp. 1, dorsal view, CMM-I-4308. Scale bar = 1 cm.

Figure 21. n. sp. 1, dorsal view, CMM-I-4312. Scale bar = 1 cm.

Figure 22. Necronectes drydeni, dorsal view, CMM-I-231. Scale bar = 1 cm.

Figure 23. Necronectes drydeni, ventral view CMM-I-231. Scale bar = 1 cm.

Figure 24. Necronectes drydeni, dorsal view CMM-I-4317. Scale bar = 1 cm.

41 Figure 25. Necronectes drydeni, ventral view CMM-I-4317. Scale bar = 1 cm.

Figure 26. Necronectes drydeni, dorsal view CMM-I-4313. Scale bar = 1 cm.

Figure 27. Necronectes drydeni, ventral view CMM-I-4313. Scale bar = 1 cm.

42 Figure 28. Necronectes drydeni, dorsal view CMM-I-4318. Scale bar = 1 cm.

Figure 29. Necronectes drydeni, ventral view CMM-I-4318. Scale bar = 1 cm.

Figure 30. Necronectes drydeni, dorsal view CMM-I-4320. Scale bar = 1 cm.

43 Figure 31. Necronectes drydeni, ventral view CMM-I-4320. Scale bar = 1 cm.

Figure 32. Necronectes drydeni, dorsal view CMM-I-4319. Scale bar = 1 cm.

Figure 33. Necronectes drydeni, ventral view CMM-I-4319. Scale bar = 1 cm.

Figure 34. Necronectes drydeni, dorsal view CMM-I-4314. Scale bar = 1 cm.

Figure 35. Necronectes drydeni, ventral view CMM-I-4314. Scale bar = 1 cm.

Figure 36. Necronectes drydeni, dorsal view CMM-I-3920. Scale bar = 1 cm.

Figure 37. Necronectes drydeni, ventral view CMM-I-3920. Scale bar = 1 cm.

45 Figure 38. Necronectes drydeni, dorsal view CMM-I-4316. Scale bar = 1 cm.

Figure 39. Necronectes drydeni, ventral view CMM-I-4316. Scale bar = 1 cm.

Figure 40. Necronectes drydeni, dorsal view CMM-I-4043. Scale bar = 1 cm.

46 Figure 41. Necronectes drydeni, dorsal view CMM-I-2941. Scale bar = 1 cm.

Figure 42. Necronectes drydeni, ventral view CMM-I-2941. Scale bar = 1 cm.

Figure 43. Necronectes drydeni, dorsal view CMM-I-3931. Scale bar = 1 cm.

Figure 44. Necronectes drydeni, ventral view CMM-I-3931. Scale bar = 1 cm.

47 Figure 45. Necronectes drydeni, dorsal view CMM-I-3996. Scale bar = 1 cm.

Figure 46. Necronectes drydeni, ventral view CMM-I-3996. Scale bar = 1 cm.

Figure 47. Cancer borealis, dorsal view CMM-I-2796. Scale bar = 1 cm.

Figure 48. Cancer irroratus, dorsal view CMM-I-2616. Scale bar = 1 cm.

Figure 49. n. sp. 2, dorsal view, barnacles attached to the left side of the carapace, CMM- I-4014. Scale bar = 1 cm.

Figure 50. n. sp. 2, ventral view, showing the left cheliped, CMM-I-4014. Scale bar = 1 cm.

Figure 51. Callinectes sapidus., dorsal view, CMM-1-3688. Scale bar = 1 cm.

Figure 52. Callinectes sapidus, ventral view, female pleon, CMM-I-3688. Scale bar = 1 cm.

Figure 53. Callinectes sapidus., dorsal view, CMM-I-3688. Scale bar = 1 cm.

Figure 54. Callinectes sapidus., ventral view, immature female pleon, CMM-I-3688. Scale bar = 1 cm.

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