434 Materials and methods


The materials examined in this study were collected at: (1) Cabeza de León, 50.21533°S, 68.52967°W (Monte León For- mation), Santa Cruz Province; (2) Playa Larralde, 42.24787°S, 64.19202°W(Puerto Madryn Formation), Chubut Province; and (3) Punta del Marqués, 45.56791°S, 67.33229°W (Chenque Formation). In addition, we examined material deposited in the Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Colección Ciencias Geológicas, collected at three sites (Estancia Meseta Chica, Estancia Lobo, and Cañadón Lobo), all located in the Bajo de San Julián, San Julián Forma- tion (Fig. 2). Material from the localities Bahía Sanguinetto and Cañadón al Deseado is housed in Museo de La Plata and lacks a precise geographic location in Santa Cruz Province. Colonies were recovered under binocular microscopes and


washed using an ultrasonic cleaner. Uncoated fragments of A. tehuelche new species were photographed in low vacuum with a scanning electron microscope (SEM) at the Servicio de Microscopía Electrónica de Barrido y Microanálisis of LIMF (Departamento de Mecánica, Facultad de Ingeniería—UNLP). Material of all other species was coated with gold-palladium and imaged with a Phillips series XL model 30 SEM at the Museo Argentino de Ciencias Naturales (MACN).


Repositories and Institutional abbreviations.—CPBA, Facultad de Ciencias Exactas y Naturales, Colección Ciencias Geológicas. MACN-In, Colección Nacional de Invertebrados, Museo Argen- tino de Ciencias Naturales. MLP, División Paleozoología Inver- tebrados -Museo de La Plata. MPEF-PI, Colección Paleontología Invertebrados, Museo Paleontológico Egidio Feruglio, and MNHN, Muséum national d'Histoire naturelle.


Systematic paleontology


Phylum Bryozoa Ehrenberg, 1831 Class Gymnolaemata Allman, 1856 Order Cheilostomata Busk, 1852


Superfamily Microporoidea Gray, 1848 Family Aspidostomatidae Jullien, 1888 Genus Aspidostoma Hincks, 1881


Aspidostoma ortmanni Canu, 1904 Figure 3.1–3.5


1900 Aspidostoma giganteum (Busk); Ortmann, p. 378 (non Eschara gigantea Busk, 1854).


1902 Aspidostoma giganteum (Busk); Ortmann, p. 67, pl. 13, fig. 4 (non Eschara gigantea Busk, 1854).


1904 Aspidostoma ortmanni nom. nov.; Canu, p. 14 (part, only Ortmann’s material from San Julián, Oven Point).


Type.—Syntype. Aspidostoma ortmanni Canu, 1904. Collection Tournouër. MNHN-F-R53493. Argentina, Punta Borja.


Description.—Colony erect, bilaminar, robust. Autozooids ordered in quincunx, subhexagonal. Autozooid length = 802 (673–911) µm;width = 459 (376–515) µm; length-to-width ratio = 1.7. Frontal surface consisting of a coarsely granular cryptocyst with protruding lateral margins and a slightly depressed central area, pierced by small, scarce, scattered pores. Cryptocyst distal to


Journal of Paleontology 92(3):432–441


the opesia-orifice with a pair of distolateral spiniform processes that are eroded inmost zooids. Cryptocyst proximal to the opesia- orifice with an inconspicuous median ridge, laterally depressed. Opesia-orifice wider than long, 100µm long × 220 µmwide, D-shaped; proximalmargin concave, everted,with a quadrangular process having a notch at each side for the passage of muscles depressing the frontal membrane. Interzooidal avicularia scarce, small, directed distally or more rarely proximally; avicularian cystide in contact with three autozooids, 131µmlong × 71 µm wide, the length about 16% of autozooid length, with triangular rostrumand an incomplete pivot bar. Autozooids in some parts of the colony with orifices obliterated by secondary calcification and perforated by small pores. Ovicells hyperstomial, globular.


Materials.—UBA, Facultad de Ciencias Exactas y Naturales, Colección Ciencias Geológicas: Santa Cruz Province, Argen- tina. Estancia Meseta Chica (CPBA No. 23690a, b; 23691), Estancia Lobo (CPBA No. 23692), Cañadón Lobo (CPBA No. 23693, 23694).


Remarks.—The fossilmaterial found byOrtmann (1900, 1902) at the ‘Mouth of Santa Cruz River’ and ‘SanJulianOven Point’ was assigned by him to Aspidostoma giganteum (Busk, 1854), an extant species currently common and widely distributed in the Magellanic region. In his first study devoted to Patagonian fossil bryozoans, Canu (1904) was of the opinion that this material was not conspecific with the extant species and therefore introduced a new species, A. ortmanni. In a later study (Canu, 1908), however, he reverted this decision and included A. ortmanni in the syno- nymy of A. giganteum. The most obvious difference between A. ortmanni and A. giganteumis the size of the autozooids,which are almost 50%larger in the Recent than in the Oligocene species. In addition, avicularia are relatively much smaller with respect to autozooids in A. ortmanni than in A. giganteum (Table 1).


Aspidostoma incrustans Canu, 1908 Figure 3.6, 3.7


1908 Aspidostoma incrustans n. sp.; Canu, p. 279, pl. 7, fig. 13. 1946 Aspidostoma incrustans Canu 1908; Buge, p. 207.


Type.—Syntype. Aspidostoma incrustans Canu, 1908. Collection Tournouër.MNHN-F-R53494. Argentina, Punta Borja.


Occurrence.—Early Miocene, Punta Borja (Canu, 1908) and Monte León Formation (see Parras et al., 2012).


Description.—Colony encrusting, the single fragment studied here consisting of 10 zooids. Zooids irregular or subhexagonal in shape, slightly longer than wide, delimited by indistinct sutures. Autozooid length = 570 (475–673) µm; width = 522 (436–614) µm; length-to-width ratio = 1.1.Cryptocyst elevated at the margin and almost flat toward the opesia-orifice, pierced by very large, abundant infundibuliform pores arranged in a quincuncial pattern. Opesia-orifice D-shaped, sunken, with a straight proximal border. Quadrangular process protruding, with a crenulated proximal margin and a notch at each side for the passage of muscles. There is a granular cryptocystal thickening separated from the quadrangular process by a slit. Distally to the opesia-orifice there may be distolateral peristomial processes with a variable degree of preservation. Avicularia and ovicells not seen.


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