Submitted: September 4th, 2019 – Accepted: May 20th, 2020 – Published online: May 23th, 2020 To link and cite this article: doi: https://doi.org/10.5710/AMGH.20.05.2020.3290 http://zoobank.org/4677401B-52B9-4B1F-91E2-F52F5485D4C3

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TWO NEW SPECIES OF PRATULUM FROM THE LOWER MIOCENE OF 1

CHILE - THE FIRST RECORDS OF PRATULUM (BIVALVIA, CARDIIDAE) 2

FROM SOUTH AMERICA 3

4

JOCELYN ROJAS, and SVEN N. NIELSEN* 5

6

Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Casilla 567, 5090000 7

Valdivia, Chile. jre2686@hotmail.com; sven.nielsen@uach.cl 8

*corresponding author 9

10

20 pages, 2 figures 11

12

Proposed header: ROJAS AND NIELSEN: MIOCENE PRATULUM FROM CHILE 13

14

Short description: Two new species of Pratulum from the Chilean lower Miocene 15

extend the genus’ geographic range to South America. 16

2

Abstract. The genus Pratulum is one of the most abundant genera of Cardiidae in 17

formations of Cenozoic age in New Zealand, Australia and Antarctica. Currently, three 18

species are known to inhabit the warm seas of Australia and New Zealand. Here, two 19

new species are described, P. kurrawchipellu sp. nov. and P. terpoorteni sp. nov., 20

extending its biogeographic distribution to South America, specifically to lower 21

Miocene localities of central to southern Chile. Also, this finding contributes additional 22

evidence that reaffirms the faunistic relationship between South America, Australia, 23

New Zealand and Antarctica during the Cenozoic, adding another genus to the list of 24

mollusks that shares its distribution among these regions. 25

26

Keywords. Pratulum. Ipun beds. Navidad Formation. Lower Miocene. 27

28

Resumen. DOS NUEVAS ESPECIES DE PRATULUM DEL MIOCENO INFERIOR 29

DE CHILE – LOS PRIMEROS REGISTROS DE PRATULUM (BIVALVIA, 30

CARDIIDAE) DE SURAMÉRICA. El género Pratulum es uno de los más abundantes 31

géneros de Cardiidae en formaciones de edades Cenozoicas en Nueva Zelanda, 32

Australia y Antártica. En la actualidad se conoce tres especies que habitan en los mares 33

cálidos de Australia y Nueva Zelanda. En este estudio, se describen dos nuevas 34

especies, P. kurrawchipellu sp. nov. y P. terpoorteni sp. nov., lo cual permite extender 35

su distribución biogeográfica a Sudamérica, específicamente a localidades del Mioceno 36

inferior del centro a sur de Chile. Además, este hallazgo contribuye con evidencias que 37

reafirman la relación faunística entre Suramérica, Australia, Nueva Zelanda y Antártica 38

durante el Cenozoico, sumando un género más a la lista de moluscos que comparte su 39

distribución entre estas regiones. 40

41

3

Palabras claves. Pratulum. Estratos de Ipun. Formación Navidad. Mioceno inferior. 42

4

43

THE bivalves of the family Cardiidae Lamarck, 1809 are a large group of heterodonts, 44

with origin in the Late Triassic and a diversity of almost 200 species (Schneider, 1995, 45

2002). The Cardiidae have been the subject of considerable taxonomic work by 46

paleontologists, who have recognized numerous subfamilies, genera, and subgenera. 47

Since the Pliocene-Pleistocene boundary, cardiids begin to decline in diversity with 48

several taxa becoming extinct (La Perna and D’Abramo, 2011). Disappearance of more 49

warm-water taxa occurred during the transition between early and middle Pleistocene 50

(0.9-0.6 Ma), when a new climatic regime with intensified glacial and interglacial 51

oscillations became stronger (Ruddiman et al., 1989; La Perna and D’Abramo, 2011). 52

The genera Pratulum Iredale, 1924 and Nemocardium Meek, 1876 are globally the 53

oldest extant groups of the family Cardiidae (Schneider, 1995, 2002; ter Poorten et al., 54

2017) and are among the few taxa that survived the last mass extinction at the end of the 55

Cretaceous (ter Poorten, 2013). The genus Pratulum is distributed from the late 56

Cretaceous until today. Species of Pratulum are known in Australia during the whole 57

Cenozoic (e.g., Darragh, 1970; Poutiers, 1992) and probably are also present in the 58

Upper Cretaceous; in New Zealand, its presence is registered from the Lower Paleocene 59

onwards (Beu and Maxwell, 1990), while on King George Island, Antarctica, it is 60

documented from the Oligocene to Lower Miocene (Beu, 2009). 61

Pratulum is one of the most omnipresent fossils in marine mudstones of the upper 62

Pliocene and the Pleistocene of New Zealand. It is a genus indicating fine-grained and 63

unconsolidated substrate rather than any particular depth-range (Beu and Maxwell, 64

1990). Today, the type species P. thetidis (Hedley, 1902) has been dredged in sand to 65

137 m (Lamprell and Whitehead, 1992), P. occidentale shells were found from 20 to 66

320 m but living animals only from around 100 m (ter Poorten et al., 2017), and P. 67

5

pulchellum (Gray, 1843) lives commonly around New Zealand in soft fine-grained 68

sediments in a wide range of habitats and depths (Beu and Maxwell, 1990). Pratulum, 69

unlike Nemocardium, apparently does not represent a Tethyan Indo-Pacific element, but 70

is limited to temperate to subtropical waters of the southern half of Australia (which 71

extends well into the western and eastern coasts) and New Zealand as well as the 72

Subantarctic zones of King George Island during the mid-Cenozoic (Poutiers, 1992). 73

According to Poutiers (1992), Pratulum is a clearly Austral-Asiatic genus of small 74

protocardiines well separated from the large species of Nemocardium. 75

Phylogenetic studies suggest that development of radial ribs on the posterior slope 76

in Cardiidae (such as Nemocardium and Pratulum) would be ancestral for the 77

evolutionary step from predominantly commarginal Mesozoic type sculpture, as in 78

Protocardia Beyrich, 1845, to a type of complete radial sculpture that developed widely 79

within Cardiidae during the Cenozoic (Schneider, 1995; La Perna and D’Abramo, 80

2011). In most Cardiidae, ribs are approximately equal in width and strength on the 81

whole shell surface, while the ribs on the posterior slope, and/or more rarely on the 82

anterior slope, may be slightly weaker or stronger in some groups (Schneider, 1995). 83

Nemocardium has been traditionally subdivided into a large number of subgenera 84

(Schneider, 1995; ter Poorten, 2013), many of which are now recognized as separate 85

genera: Frigidocardium Habe, 1951, Habecardium Glibert and van de Poel, 1970, 86

Lophocardium Fischer, 1887, Lyrocardium Meek, 1876, Microcardium Keen, 1937, 87

Pratulum, and Trifaricardium Kuroda and Habe, 1951. Extensive phylogenetic analyses 88

were done at the generic level of the family Cardiidae (Schneider, 1995, 1998a, 1998b, 89

2002), however to date there is still no clarity about the phylogenetic relationships of 90

some groups, especially regarding the genera Nemocardium and Pratulum (ter Poorten 91

et al., 2017). This is mainly due to the lack of soft tissue of both taxa (ter Poorten, 92

6

2013). Therefore, this work follows the taxonomy proposed by Schneider (1995) and ter 93

Poorten (2013), where Pratulum is considered as a separate genus and not as a subgenus 94

of Nemocardium. This separation is due to the fact that Nemocardium shows typical ribs 95

and pronounced tubercles on the posterior part of the shell, unlike Pratulum, because 96

according to Poutiers (1992: 142): “[...] the outer surface has two clearly differentiated 97

areas as in Nemocardium s.s. but, in Pratulum, radial ribbing is not limited to the 98

posterior area. Moreover, the anterior and median areas of Pratulum spp. have a fine 99

secondary sculpture of irregularly concentric, anastomosing threads crossing the radial 100

ribs. The marginal crenulations are not clearly stronger posteriorly as they are in 101

Nemocardium but, as in that genus, the crenulations do correspond with the radial 102

sculpture”. Nemocardium species also are markedly larger than Pratulum species. The 103

morphological characteristics of the specimens under study are thus consistent with 104

those indicated for Pratulum. 105

Although Cardiidae is a relatively diverse and locally abundant group in the 106

Cenozoic of southern South America, with described representatives of “Cardium” 107

(Punta Arenas, Guayacan, Coquimbo, Tubul, Santa Cruz, Lebu, Lota, Chiloé, all 108

“Tertiary”, Philippi, 1887, 1897), Trachycardium (Argentina, Miocene; del Rio and 109

Martinez, 1998; Navidad, Miocene; Griffin and Nielsen, 2008), Patagonicardium 110

(Aisén, Oligocene-Miocene; Frassinetti and Covacevich, 1999), Dinocardium 111

(Argentina, Miocene; Griffin and Nielsen, 2008), Hedecardium (Argentina, Tertiary; 112

Griffin and Nielsen, 2008), and Loxocardium, (Argentina, Tertiary; del Rio, 2002), 113

there are currently no records of the genus Pratulum from South America. 114

Institutional abbreviation. SGO.PI., invertebrate paleontology collection of the Museo 115

Nacional de Historia Natural in Santiago, Chile. 116

GEOLOGIC SETTING 117

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The studied material comes from two geological units, the Navidad Formation in 118

the Libertador General Bernardo O'Higgins Region, Cardenal Caro Province, and the 119

Ipún beds from the Los Chonos Archipelago in the Aysén Region of central and 120

southern Chile, respectively (Fig. 1). 121

The Navidad Formation is composed of sandstones, mudstones, conglomerates 122

and coquinas. It overlies the Punta Topocalma Formation (Cecioni, 1978; Encinas et al., 123

2014) and underlies the Licancheu Formation with an erosional contact (Encinas et al., 124

2006). The most important distinctive character of this formation is the predominant 125

alternation of sandstone and mudstone beds of centimeter to meter thickness (Encinas et 126

al., 2006). The localities Las Brisas (LBZ: 33°46'49"S, 71°47'38"W) and Punta Perro 127

(PPN: 33°54'23"S, 71°50'18"W) (Fig. 1 B) both consist of yellowish to orange-brown 128

fossiliferous sandstone lenses in the coastal bluffs belonging to the Navidad Formation 129

(see Encinas et al. 2006; Finger, 2013). They both contain the classic Navidad fauna 130

described by several authors (Darwin, 1846; Tavera, 1979; Kiel and Nielsen, 2010) of 131

more shallow-water affinity (Finger et al., 2007) including many typical gastropod taxa 132

(e.g., Griffin and Nielsen, 2008; Kiel and Nielsen, 2010). The beds at LBZ, in contrast 133

to PPN, contain abundant Pinna semicostata Philippi, 1887. 134

The southern study region is situated in the Los Chonos Archipelago, on the 135

islands Ipún, Lemo, and Stokes (Fig. 1 C). The lower Miocene deposits, informally 136

named Ipún beds by Encinas et al. (2018), are underlain with unknown contact by the 137

Chonos Metamorphic Complex (Hervé and Fanning, 2001) and discordantly overlain by 138

possibly Pleistocene deposits, as can be seen on the northern coast of Ipún Island 139

(Nielsen and Encinas, 2014). The lower Miocene deposits contain the same mollusk 140

fauna as is present in the Navidad Formation and its equivalents (Kiel and Nielsen, 141

2010). Towards the east, on Stokes and Lemo islands, the lower Miocene deposits were 142

8

deposited in relatively shallow marine environments, but they were deposited in 143

increasingly deeper-water facies towards the west on Ipún Island (Nielsen and Encinas, 144

2014). 145

The Stokes Island locality (STO 01: 44°39'5,30"S, 74°40'7,86"W) is situated at 146

the extreme northwestern corner of the western peninsula (localities 051083.1 and 147

310884.1 of Frassinetti, 2001), opposite Lemo Island, representing today’s intertidal 148

platform. The lithology is medium to coarse-grained fossiliferous sandstones with 149

cemented finer intercalations (Frassinetti, 2001). The fauna reported by Frassinetti 150

(2001) includes Pinna semicostata, Trachycardium puelchum, Mactra pusilla, Natica 151

striolata, Penion darwinianus, Scaphander remondi, Trochus poeppigii?, and 152

Lamprodomina dimidiata?. According to Tavera (1979) and Covacevich and Frassinetti 153

(1986), these are exclusive species of the Navidad Formation and its equivalents. 154

The Ipún Island locality (IPN 02: 44°39'6,34"S, 74°42'55,54"W) is situated at the 155

southeastern tip of the island and corresponds to locality 1 of Frassinetti (2004), 156

representing today’s intertidal platform. The lithology is dark grey mudstone to fine 157

sandstone with low fossil content. The fauna reported by Frassinetti (2004) includes 158

species such as Neilo aff. N. volckmanni, Mactra pusilla, Turritella ambulacrum (= T. 159

pseudosuturalis), Penion darwinianus and Lamprodomina dimidiata, which according 160

to Tavera (1979) and Covacevich and Frassinetti (1986), can be considered as exclusive 161

to the Navidad Formation and its equivalents. Fuenzalida and Martínez-Pardo (1970) 162

indicated the presence of planktonic Foraminifera, including the species Sphaeroidinella 163

seminulina, Praeorbulina sicana, and Fohsella praefoshi, while Stott and Webb (1986) 164

listed Globorotalia miozea, Praeorbulina glomerosa, Globoquadrina dehiscens, and 165

Catapsydrax dissimilis, together indicating an age between about 17-18 and 12-13 Ma 166

(Frassinetti, 2004). 167

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SYSTEMATIC PALEONTOLOGY 168

Class BIVALVIA Linnaeus, 1758 169

Superorder HETEROCONCHIA Gray, 1854 170

Clade HETERODONTA Neumayr, 1884 171

Order VENERIDA Gray, 1854 172

Family CARDIIDAE Lamarck, 1809 173

Genus Pratulum Iredale, 1924 174

175

Type species. Cardium striatulum var. thetidis Hedley, 1902, by original designation; 176

Extant, off New South Wales, Australia. 177

178

Pratulum kurrawchipellu sp. nov. 179

Figure 2 180

Etymology. From the native Mapuzungun language, kurrawchi meaning turned into 181

stone and pellu mollusk or seafood. Although the Chonos Archipelago is located south 182

of the Mapuche territory, the species presumably also lived further north. 183

Type material. Holotype SGO.PI.6529 (IPN 02), semi-articulated valves, left valve 184

length 34 mm, height 31 mm; paratype SGO.PI.6530 (STO 01), length 25 mm, height 185

26 mm. 186

Diagnosis. A species of Pratulum with radial sculpture divided into three areas: a 187

posterior area with well-separated fine ribs with tubercles in intercostal spaces, a central 188

area with thick and dense ribs that gradually become more separated and thinner ribs 189

than the central ones. Commarginal sculpture present only on central and anterior areas. 190

Stratigraphic and geographic occurrence. Localities IPN 02, STO 01, Ipún Beds, Los 191

Chonos Archipelago. The Ipún beds were correlated to the Navidad Formation based on 192

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macrofauna (Frassinetti, 2001, 2004; Kiel and Nielsen, 2010; Nielsen and Encinas, 193

2014) and are therefore regarded to be lower Miocene (Nielsen and Glodny, 2009; 194

Finger, 2013). The type locality is on Ipún island. 195

Description. The shell is circular, globose and inequilateral, with the prominent umbo 196

slightly prosogyrate. Its posterior end is more extended than the anterior one. The 197

anterior margin is well-rounded while the posterior margin is more straight to almost 198

truncated. The union of the ventral and posterior margins forms a smooth curve (Figs. 199

2.1). The posterior third of the shell is marked by a sharp change in radial sculpture, 200

which defines the posterior area. The posterior radial sculpture consists of 16 - 24 very 201

narrow and well-spaced ribs, which become diffuse towards the postero-dorsal margin. 202

In the intercostal spaces there are small blunt-tipped tubercles that emerge from the 203

anterior limit of each rib (Fig. 2.2 and 2.9). Tubercles are spaced approximately every 1 204

mm within one interspace. On the anterior area, there is radial ornamentation consisting 205

of about 10 - 17 thin and more widely spaced ribs (Fig. 2.3 and 2.8), while in the center 206

of the valve, the radial ornamentation becomes wider, denser and subrectangular to 207

subrounded in cross-section (20 - 40 ribs), with intercostal spaces narrower than those 208

observed on the posterior and anterior areas (Fig. 2.7). Commarginal sculpture consists 209

of fine, dense and rounded, wavy crenulating ridges within interspaces on the central 210

and anterior areas (Figs. 2.7 and 2.8) giving the interspaces a pitted appearance. 211

Commarginal sculpture is not present in interspaces of the posterior area. The hinge is 212

covered or broken in all specimens. In spite of only partial preservation, it is possible to 213

identify in the left valve a wide and solid hinge plate, made up of a large cardinal tooth 214

in the shape of a hook and a prominent lateral tooth with a lamellar aspect curving back 215

towards the dorsal margin (Figs. 2.5 and 2.6). 216

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Discussion. The general shell outline, globose aspect, and sculpture of the posterior area 217

are similar in Nemocardium and Pratulum. However, radial sculpture in Pratulum is not 218

limited to the posterior area as in most species of Nemocardium (Poutiers, 1992). Also, 219

the anterior and central areas in Pratulum have a secondary sculpture of fine, irregular, 220

anastomosing commarginal lines that cross the radial ribs, forming crenulations. 221

Marginal crenulations are not clearly stronger posteriorly as is the case in Nemocardium 222

but, as in this latter genus, they correspond to radial sculpture (Poutiers, 1992). 223

Therefore, the species described herein is placed in Pratulum. 224

Pratulum kurrawchipellu sp. nov. is similar to Nemocardium cyprium (Brocchi, 1814) 225

from the Pliocene of Italy (La Perna and D’Abramo, 2011) and Pratulum pulchellum 226

(Gray, 1843) from the upper Pliocene to Recent of New Zealand (Beu and Maxwell, 227

1990) in having crenulation through the intersection of growth lines with radial 228

sculpture, visible in the interspaces between ribs. However, while in the two latter 229

species these crenulations extend over the whole shell surface, they are only present on 230

the central and anterior parts in P. kurrawchipellu sp. nov. Another distinctive character 231

of Nemocardium is the position of the tubercles, which usually are situated on the ribs, 232

as for example in N. bechei (Reeve, 1847) (upper Pliocene to Recent, Indian and West 233

Pacific oceans; La Perna and D’Abramo, 2011) and N. cyprium. Pratulum 234

kurrawchipellu sp. nov., on the other hand, has tubercles on the anterior side of the 235

posterior ribs, similar to those in Microcardium peramibile (Dall, 1881) (Recent, deep 236

and cold waters of Rhode Island, Florida; Schneider and Carter, 2001) and N. carteri 237

Maxwell, 1992 from the Eocene of New Zealand (Maxwell, 1992); the latter differs 238

from P. kurrawchipellu sp. nov. by its larger size, radial sculpture and prominent 239

tubercles. Another difference is that radial ribs in most Nemocardium species are much 240

more prominent at the posterior end, while P. kurrawchipellu sp. nov. has more slender 241

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ribs at the posterior end than on the rest of the shell, similar to those of P. quinarium 242

Marwick, 1944 from the middle Miocene to early Pliocene of New Zealand (Saether et 243

al., 2016); P. quinarium has no tubercles on its posterior area. 244

In general, species of both Nemocardium and Pratulum have their sculpture 245

differentiated into two areas (Poutiers, 1992; Schneider, 1995; ter Poorten, 2013). The 246

posterior area has prominent ribs and small tubercles, while the rest of the surface can 247

be almost smooth with fine growth lines as in N. patulum (Hutton, 1873) (upper 248

Oligocene to middle Miocene of New Zealand; ter Poorten, 2013) or, in a few species, 249

covered with dense fine ribs as in N. auberti Abrard, 1946 (Miocene of Vanuatu; ter 250

Poorten, 2013) or P. pulchellum. In P. kurrawchipellu sp. nov., however, it is possible 251

to differentiate three areas: a posterior area with well-separated fine ribs and tubercles, a 252

central area with dense broad ribs, and an anterior area with ribs finer than the central 253

ones and more separated than in both central and posterior areas. This pattern 254

distinguishes Pratulum kurrawchipellu sp. nov. from all other species. 255

256

Pratulum terpoorteni sp. nov. 257

Figure 3 258

Etymology. After Jan Johan ter Poorten (Field Museum of Natural History, Chicago, 259

USA), renowned expert on cardiid bivalves and citizen scientist. This dedication 260

highlights the importance of citizen scientists in biodiversity studies. 261

Type material. Holotype SGO.PI.6531 (LBZ), left valve, length 12 mm, height 10 mm; 262

paratype SGO.PI.6532 (PPN), length 4 mm, height 5.5 mm. 263

Diagnosis. Species of Pratulum with radial and commarginal ornamentation of equal 264

strength in anterior and central areas, forming a cancellate pattern with narrow 265

13

interspaces. Posterior area with finer and sharper ribs than on the rest of the shell, with 266

small blunt tubercles. 267

Stratigraphic and geographic occurrence. Localities PPN and LBZ, Navidad 268

Formation of Burdigalian age, lower Miocene (Nielsen and Glodny, 2009; Finger, 269

2013). The type locality is Las Brisas (LBZ). 270

Description. The shell is small, circular to sub-circular, globose, and inequilateral with 271

the prominent umbo slightly prosogyrate. Its posterior end is more extended than the 272

anterior one. The anterior margin is well-rounded while the posterior margin is slightly 273

straighter. The union of the anterior, ventral and posterior margins forms a well-rounded 274

curve (Fig. 3.1). The posterior third of the shell is marked by a sharp change in 275

sculpture, which defines the posterior area. The posterior radial sculpture consists of 16 276

– 20 narrow, well-spaced ribs, which become diffuse towards the postero-dorsal margin 277

(Fig. 3.2). In the intercostal spaces there are small blunt-tipped tubercles that emerge 278

from the anterior limit of each rib, being concentrated mostly on the surface of the 279

postero-dorsal area (Fig. 3.5). On the remaining anterior and central surface, radial 280

ornamentation is composed of about 45 to 50 narrow, closely spaced, subrounded ribs 281

(Fig. 3.3). These are crossed by commarginal cords of the same width and narrow 282

spacing. Some commarginal cords become distorted and lose continuity (Fig. 3.4). 283

There is also a progressive change in rib separation, increasing in spacing from the 284

antero-ventral to the antero-dorsal areas. The ribs disappear in the lunular zone, with 285

only commarginal ornamentation remaining, decreasing and almost smooth (Fig. 3.6). 286

Internal characters are unknown. 287

Discussion. Pratulum terpoorteni sp. nov. differs from P. kurrawchipellu sp. nov. in 288

having commarginal and radial ornamentation of the same size. Radial ribs cross 289

commarginal ornamentation, generating a grid pattern, while in P. kurrawchipellu sp. 290

14

nov. commarginal ornamentation is fine, lamellar, and continuous. Pratulum terpoorteni 291

sp. nov. is morphologically similar to P. quinarium Marwick, 1944, both being small, 292

with a similar outline, dense radial ribs that generate narrow interspaces, and 293

commarginal ornamentation crossing radial ribs. They differ in their ornamentation of 294

the posterior area, which has no tubercles in P. quinarium (Beu and Maxwell, 1990; 295

Saether et al., 2016). Other species similar to P. terpoorteni sp. nov. are Nemocardium 296

cyprium and P. thetidis, both with a similar outline and blunt tubercles in the posterior 297

area. However, N. cyprium has radial ornamentation with shallow and well 298

differentiated growth lines (La Perna and D’Abramo, 2011), while radial ornamentation 299

in anterior and central areas of P. terpoorteni sp. nov. is crossed by commarginal 300

ornamentation of the same width. In P. thetidis commarginal ornamentation is weak, 301

with ribs on the posterior area of the same width as those on the anterior and central 302

areas, the posterior area has slightly wider interspaces, and tubercles cover a larger part 303

of this area, while in P. terpoorteni sp. nov. the tubercles are limited to a narrower 304

postero-dorsal area. 305

DISCUSSION 306

The genus Pratulum is reported for the first time from lower Miocene deposits of Chile, 307

thus extending its biogeographical range from Australia and New Zealand to South 308

America. Considering their morphological differences, it seems reasonable to follow 309

Poutiers (1992) and ter Poorten (2013) in considering Pratulum at the genus level and 310

different from Nemocardium. 311

The genus Pratulum is a warm-water representative, which agrees with conditions 312

previously proposed for the Navidad Formation and equivalent units based mostly on 313

gastropod taxa (Nielsen and DeVries, 2002; Groves and Nielsen, 2003; Nielsen, 2004; 314

Nielsen and Frassinetti, 2007; Nielsen and Glodny, 2009). The occurrence of Pratulum 315

15

in Navidad-aged deposits of Chile strengthens the previously established links between 316

Chilean and New Zealand-Australian faunas (Nielsen, 2005; Beu, 2010; Beu et al., 317

1997). 318

ACKNOWLEDGEMENTS 319

This work was financially supported by Fondart Nacional grant 495612 financing the 320

postgraduate studies of JR and Fondecyt regular grant 1150664 “Miocene diversity 321

along the coast of central to southern Chile across multiple taxa” to SNN. Cecilia 322

Sandoval Tripailaf and family are thanked for advice on correct usage of Mapuzungun. 323

Constructive comments of reviewers Alan Beu and Damián Pérez significantly 324

improved the manuscript. Alan Beu is additionally thanked for polishing the English 325

and Jan Johan ter Poorten for sharing some opinions about our materials. 326

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497

Figure captions 498

Figure 1. Location of study areas, asterisks mark the localities from where the studied 499

material is collected. A. General map. B. Navidad area. C. Los Chonos area. 500

Figure 2. Lower Miocene Chilean Pratulum kurrawchipellu sp. nov. 1-5, 7-9, holotype 501

SGO.PI.6529 from Ipún island, 6 paratype SGO.PI.6530 from Stokes island. 1, lateral 502

view of left valve, bar = 10 mm. 2, posterior view of left valve, bar = 10 mm. 3, anterior 503

view of left valve, bar = 10 mm. 4, , lateral view of right valve, bar = 10 mm. 5, hinge 504

of left valve, bar = 10 mm. 6, hinge of right valve, bar = 10 mm.7, sculpture of the 505

central area of the valve where a thickening of the ribs and commarginal lamellae is 506

observed, bar = 5 mm. 8, sculpture of the anterior area, decreasing of thickness of the 507

ribs and continuity of the commarginal lamellae, bar = 5 mm. 9, sculpture of the 508

posterior area, tubercles are observed on the anterior side of the ribs, bar = 5 mm. 509

Figure 3. Lower Miocene Chilean Pratulum terpoorteni sp. nov. 1-8, holotype 510

SGO.PI.6531 from the Navidad Formation at Las Brisas (LBZ). 1, lateral view of left 511

valve, bar = 5 mm. 2, posterior view of left valve, bar = 5 mm. 3, anterior view of left 512

valve, bar = 10 mm.4, sculpture of the central area of the valve with narrow rounded 513

ribs and narrow interspaces, crossed by commarginal cords of the same thickness, 514

forming a lattice surface, bar = 5 mm. 5, sculpture of the posterior area, tubercles are 515

observed on the anterior side of the ribs, bar = 5 mm. 6, sculpture of the anterior area, 516

decreasing of thickness of the ribs and continuity of the commarginal cords, this 517

sculpture disappears in the lunular area leaving only commarginal sculpture in almost 518

smooth tenuous form, bar = 5 mm. 7, ventral, crenulate shell rim. 8, hinge of left valve, 519

bar = 5 mm. 520