Boletín de la Sociedad Geológica Mexicana

Volumen 71, núm. 3, 2019, p. 819-830 



Short note

Clypeasteroids (Echinodermata: Echinoidea) From the Cretaceous In Mexico?

Alejandra Martínez-Melo


Colección Nacional de Paleontología, Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria. C.P. 04510, Ciudad de México, México.

UMR 7207, Centre de Recherche en Paléontologie - Paris, Muséum National d’Histoire Naturelle. 8 rue Buffon, CP 38, 75005 Paris, France.

This email address is being protected from spambots. You need JavaScript enabled to view it.



It is currently considered that the origin of the order Clypeasteroida occurred during the Cretaceous, with the stem group that includes the families Faujasiidae, Plasiolampadidae, Conoclypeidae, and Oligopygidae. Nevertheless, there are taxonomic reports of Cretaceous echinoids from Mexico, which also include species of the Echinarachniidae and Mellitidae families. The present paper reviews and updates the records of the Cretaceous clypeasteroids in Mexico. Specimens belonging to the order Clypeasteroida were located in national and international collections, which also provided taxonomic and paleobiogeographic data. Three species, Hardouinia aequorea, Hardouinia potosiensis, and Phyllobrissus burckhardti, are illustrated and cataloged in two of the 11 genera in family Faujasiidae. The previous records of families Echinarachniidae and Mellitidae are incorrect, coinciding with the current hypothesis on the origin of the Clypeasteroida order. Invalid catalog numbers published for the type series of Encope michoacanensis were corrected according to the Colección Nacional de Paleontología database.

Keywords: Faujasiidae, Hardouinia aequorea, Hardouinia potosiensis, Phyllobrissus burckhardti, Encope michoacanensis.



Actualmente se considera que el origen del orden Clypeasteroida se dio durante el Cretácico, con el grupo basal que incluye las familias Faujasiidae, Plasiolampadidae, Conoclypeidae y Oligopygidae. Sin embargo, hay reportes taxónómicos sobre los equinoideos del Cretácico en México que también incluyen especies de las familias Echinarachniidae y Mellitidae. En el presente trabajo se revisan y actualizan los registros de clypeasteroideos del Cretácico en México. Con una revisión bibliográfica exhaustiva se localizaron ejemplares del orden Clypeasteroida albergados en colecciones nacionales e internacionales, de los que se provee información taxonómica y paleobiogeográfica. Tres especies, Hardouinia aequorea, Hardouinia potosiensis y Phyllobrissus burckhardti, son ilustradas y catalogadas en dos de los 11 géneros de la familia Faujasiidae. Los registros previos de las familias Echinarachniidae y Mellitidae son incorrectos, coincidiendo con la hipótesis actual del origen del orden Clypeasteroida. Se corrigen los números de catálogo publicados para la serie tipo de Encope michoacanensis de acuerdo con la base de datos de la Colección Nacional de Paleontología.

Palabras clave: Faujasiidae, Hardouinia aequorea, Hardouinia potosiensis, Phyllobrissus burckhardti, Encope michoacanensis.


1. Introduction

Alexander Agassiz (1874) created the order Clypeasteroida to include the burrowing flat sea urchins, commonly named sand dollars. These costal worldwide inhabitants have an important fossil record along the Cenozoic, including some important index species (Mooi, 1987). The origin and composition of clypeasteroids has been debated for decades.

Durham (1955) and Seilacher (1979) pointed out that the family Fibulariidae, previously named by Duncan (1889), includes the oldest clypeasteroids; hence, the order Clypeasteroida arose in the Early Cretaceous (Table 1). Contrary, Kier (1962), and later Smith (1984), thought that the late Paleocene genus Togocyamyus Oppenheim, 1915, from West Africa, was the first clypeasteroid representative; consequently, this order is entirely restricted to the Cenozoic.


Table 1. Order Clypeasteroida according to different authors, showing inconsistencies between approaches.


The paleontological age estimates, based on older fossils for the origin of order Clypeasteroida using molecular clocks (Smith et al., 2006), are 100–105 Ma (Albian, Cretaceous). This statement supports the study of the post-Paleozoic echinoids phylogeny (Kroh and Smith, 2010), which reveals the monophyletic nature of Clypeasteroida, including 4 and 17 taxa as stem and crown families, respectively. Here again, the origin of this order is pulled back to the Cretaceous because the extinct family Faujasiidae, erected by Lambert, 1905 (now involving the family Stigmatopyginae Smith and Wright, 2000), includes Cenomanian representatives (Table 1).

The composition and relationships of the Clypeasteroida have not been fully determined constitute problematic and unfinished tasks. Kroh and Smith (2010) published the most comprehensive phylogenetic study of this group. These authors claimed, although weakly supported, that the Faujasiidae represents a stem family of the order Clypeasteroida. Other less-extensive studies, performed with more restricted scopes, suggest alternative taxonomical compositions of this order, in which the Faujasiidae is excluded (e.g., Durham, 1955; Kier, 1982; Smith, 1984). Currently, it is desirable to contrast these different ideas about the taxonomical composition of the order Clypeasteroida. However, any effort in that direction goes beyond the aim of this work. Therefore, here the family Faujasiidae is considered part of the order Clypeasteroida as it was concluded by Kroh and Smith (2010).

Cretaceous marine sediments of Mexico bear a potentially important fossil record of clypeasteroids, whose taxonomy must be updated following the latest studies (Wang, 1984; Mooi, 1987; Mooi, 1989; Kroh and Smith, 2010; Smith and Kroh, 2011). Nieto and García (2006) published a brief review of the Mexican echinoids, which was only based in a literature search without the direct review of the available specimens; that study enlists the occurrence of 65 echinoids species in different Cretaceous localities throughout Mexico, 20 regular and 45 irregular echinoids, including the following clypeasteroids: Clypeaster, Encope L. Agassiz, 1840, Haimea Michelin, 1851 and Astrodapsis.

The aim of this work is to review the Cretaceous fossil record of Clypeasteroida from Mexico based on a careful anatomical review of the specimens deposited in different national or foreign paleontological collections, as well as to sort, recover, and update their taxonomic and geologic data.


2. Materials and Methods

2.1. Institutional abbreviations

The fossils of clypeasteroids from the Mexican Cretaceous referred in this study are deposited in different collections, whose abbreviations are the following:

  • IGM, Instituto Geológico de México (previous name of the Instituto de Geología, UNAM) that houses the Colección Nacional de Paleontología (CNP) in its Museo María del Carmen Perrillat Montoya, Ciudad Universitaria, Mexico City, Mexico.
  • MNHN, Muséum National d’Histoire Naturelle, Collection des échinodermes fossiles, Paris, France.
  • USNM-PAL, National Museum of Natural History, Paleotological Collection, Smithsonian Institute, Washington, USA.


2.2. observed specimens

This work includes the review of specimens belonging to order Clypeasteroida deposited in different collections: Astrodapsis bajasurensis Squires and Demetrion IGM 5926-5932, Clypeaster pileus Israelsky IGM 2553, Clypeaster rogersi (Morton) IGM 2554, Encope grandis subsp. inezana Durham IGM 2825-2827, Encope loretoensis Durham IGM 8150-8151, Encope michoacanensis Durham IGM 7057-7061, Encope perspective Agassiz IGM 7062, Encope shepherdi Durham IGM 2822-2824, Encope tatetlaensis Böse IGM 147-148 and IGM 7154, Haimea bajasurensis Squires and Demetrion IGM 5934-5937, Hardouinia aequorea (Morton) USNM-PAL 464465-464466, 464468, 464470-464473, USNM-PAL, Hardouinina potosiensis Lambert MNHN F.J01116 and Petalobrissus burckhardti Lambert USNM-PAL 108380. One specimen of Hardouinia aequorea from the Regional Collection (CNP, IGM, UNAM) was determined, described, and illustrated. The taxonomical identities of the specimens studied were redetermined using the criteria of Kroh and Smith (2010) and Smith and Kroh (2011).


3. Results

3.1. Paleontological systematics

Class Echinoidea Leske, 1778

Order Clypeasteroida A. Agassiz, 1872

Stem group Clypeasteroida

Family Faujasiidae Lambert, 1905

Subfamily Stigmatopyginae Smith and Wright, 2000

Genus Hardouinia Haime in d’Archiac and Haime, 1853


Synonymous. Hardouinia Haime in d’Arvhiac and Haime, 1853, p. 214. Pomel, 1883, p. 65. Cooke, 1942, p. 6; 1953, p. 19.

Echinanthus Desor, 1858, p. 295.

Gonioclypeus Emmons, 1858, p. 309.

Australanthus Bittner, 1892, p. 20. H.L. Clark, 1946, p. 357. Mortensen, 1948, p. 222.

Cassidulus (Hardouinia) Gregory, 1891, p. 436.

Procassidulus (Hardouinia) Lambert and Thiéry, 1921, p. 362.

Type species. Pygorhynchus mortonis Michelin, 1851, p. 240 by monotypy (Cooke, 1953).

Stratigraphic range. Upper Cretaceous (Turonian to Maastrichtian, Smith and Kroh, 2011).


Hardouinia aequorea (Morton, 1834)

Figure 2, A–D.


Synonymous. Cassidulus aequoreus Morton, 1834, p. 76, fig. 3.14.

Type material. Specimen from the ferruginous sand, Prairie Bluff, Alabama, USA, with no catalog number available, illustrated by Morton (1834, fig. 3.14). Probably deposited in the Philadelphia Academy of Natural Sciences.

Description. Test subpentagonal, elongated. Aboral surface convex, oral surface flat and slightly sunken toward the peristome. Ambulacra narrow and continue toward the peristome. Phyllodes surrounding the peristome. Interambulacra wide and covered with small tubercles. Periproct aboral, sunken in a furrow, covering one third of the posterior diameter. Peristome pentagonal, surrounded by a floscele.

Examined material. USNM-PAL 464465, 464466, 464471 and 464472, from the Upper Cretaceous (Maastrichtian) sediments of Prairie Bluff Chalk, Alabama, USA. USNM-PAL 464468, 464470 and 464473, from Upper Cretaceous (Maastrichtian), Prairie Bluff Chalk, Mississippi, USA.

Distribution. Cárdenas Formation, San Luis Potosí, Mexico. Lagunar system, with low energy and storm deposits (Sánchez-Rodríguez, 1997). It has been reported in Navesink Marl, Group Monmouth, New Jersey and Ripley Formation (Upper Cretaceous), Alabama, USA (Sánchez-Rodríguez, 1997).


Hardouinina aequorea (Morton, 1834) IGM 6259

Figure 1, Table 2.


Description. Aboral surface rounded. Apical system monobasal, slightly anterior, concurring with the apex; with four genital pores, G3 towards the front. Petaloid ambulacra with similar length; ambulacra III close to ambitus. Petaloids with internal pores elliptical and external pores slit-shaped, connected by a slightly shallow channel. Ambulacra with outer pore elongated transversely; no visible pores beyond ambulacra. Periproct aboral, visible from the top, almost reaching the ambitus; triangular, elongated vertically, sunken in a furrow. Oral surface slightly sunken longitudinally. Peristome slightly anterior, pentagonal, surrounded by a floscele. Bourrelets tooth-like, projecting into and over the peristome. Phyllodes, wide, single pored; the inner series straight, with rounded small pores; the outer series arranged in a broad arc, with elliptical pores.


Figure 1. Hardouinia aequorea IGM 6259. Length: 52.18 mm; height: 22.06 mm; width: 42.41 mm. Late Cretaceous. Cárdenas, San Luis Potosí (21°38’22’’ N, 99°38’22’’ W). Collected by Ralph L. Myers, 1966. A. Aboral view, B. Oral view, C. Petaloid ambulacra, D. Posterior view, E. Lateral view (right), F. Phyllodes.


Observations. Hardouinia aequorea differs from Australanthus and Petalobrissus by having flat test and elongated ambulacra. It also diverges from Hardouinia potosiensis in the position of the periproct. In H. potosiensis the petaloids do not reach the periproct, contrary to the posterior petaloids in H. aequorea. The holotype has a subconical test, but without specimens to compare, this could be either a regular shape or the result of the fossilization process.


Table 2. Morphometric data (mm) of Hardouinia aequorea IGM 6259.



Locality. IGM-locality 956. Cárdenas, San Luis Potosí (21°38’22’’N, 99°38’22’’W); Upper Cretaceous, Campanian–Maastrichtian (Ferrusquía-Villafranca et al., 2016). Collected by Ralph L. Myers, 1966.

Hardouinina potosiensis Lambert, 1936

Figure 2, E–G.

Figure 2. Upper Cretaceous Faujasiidae from Mexico. Hardouinia aequorea (Morton, 1834); USNM-PAL 464465. A. Aboral view, B. Oral view, C. Lateral view (left), D. Posterior view. Hardouinina potosiensis Lambert, 1936 (Holotype MNHN F.J01116, Credits MNHN, 2017). E. Aboral view, F. Oral view, G. Posterior view. Petalobrissus burckhardti Lambert, 1936 (USNM-PAL108380). H. Aboral view, I. Oral view, J. Lateral view (left), K. Posterior view. 


Type species. Echinobrisus setifensis Cotteau, 1866, p. 151 by original designation (Kier, 1962).

Stratigraphic range. Upper Cretaceous (Turonian to Maastrichtian, Smith and Kroh, 2011).

Type material. Holotype MNHN L.19.773. Coniacian (Upper Cretaceous) sediments of the Cárdenas Formation, San Luis Potosí, Mexico (Lambert, 1936, pp. 5–6, figs. 1.2–1.4)

Description. Test large, oval, rounded at the anterior rear, slightly elongated. Aboral surface subconic. Apical system anterior, with four genital pores. Petaloid ambulacra, narrow, short, lanceolate and distally closed; posterior ambulacra not reaching the periproct. Periproct elongated and pointy. Oral surface slightly concave towards subcentral peristome. Oral area with bourrelets and phylodes.

Examined material. Holotype MNHN F.J01116. Cárdenas Formation, San Luis Potosí, Mexico. Upper Cretaceous, Campanian–Maastrichtian (Ferrusquía-Villafranca et al., 2016).

Distribution. Cárdenas Formation, San Luis Potosí, Mexico. (Lambert, 1936; Myers, 1968).


Genus Petalobrissus Lambert and Thiéry, 1921

Petalobrissus burckhardti Lambert, 1936

Figure 2, H–K.


Synonymous. Phyllobrissus cubensis Cooke, 1953, p. 17, figs. 17.11–17.14.

Type material. Holotype MNHN L.19.775. Cretaceous, Ocozocuautla, Chiapas, Mexico.

Description. Test oval, slightly wider at the posterior rear. Aboral surface slightly inflated. Oral surface flat, slightly concave at the peristome. Petaloid ambulacra short, reaching half the distance between the apical system and the ambitus. Apical system anterior, with four genital pores and a central large madreporite (Cooke, 1953).

Examined material. Phyllobrissus cubensis USNM-PAL 108380. Ocozocuautla, Chiapas, Mexico. Cretaceous, Senonian.

Distribution. Ocozocuautla, Chiapas (Cooke, 1953). Cretaceous, Upper Senonian (Kier and Lawson, 1978).


4. Discussion

Families Faujasiidae, Echinarachniidae, Clypeasteridae, and Mellitidae are wrongly included in the most recent revision on Cretaceous Echinoids in Mexico (Nieto and García, 2006). The specimens exist in the referred collection, but do not correspond to Cretaceous localities (Table 3).

Table 3. Species of clypeasteroids reported in the most recent revision of Cretaceous echinoids in Mexico (Nieto and García, 2006).

*Species present in the National Collection of Paleontology (IGM). 


Genus Astrodapsis is included in family Echinarachniidae, and genera Clypeaster and Encope in family Mellitidae. Both families are classified in the crown group of infraorder Scutelliformes Haeckel, 1896. Family Echinarachniidae has been reported from the middle Eocene to present, with recent species reported in North Pacific (from Japan to California, USA) (Kroh and Smith, 2010; Smith and Kroh, 2011). Family Mellitidae originated during early Miocene (Kroh and Smith, 2010) and includes recent species reported in Central and South America and the Caribbean Sea (Smith and Kroh, 2011).

Durham (1994) described Encope michoacanensis using invalid catalog numbers from the National Paleontological Collection (IGM). We include the catalog numbers used in the original references and the corrected catalog numbers used in the National Paleontological Collection (Table 4).

Table 4. Data of the clypeasteroids reported in Nieto and García, 2006 with amendments in catalog numbers.

NA: Information not Available. 


5. Conclusions

We report three species of clypeasteroids for the Cretaceous in Mexico: Hardouinia aequorea, Hardouinia potosiensis, and Phyllobrissus burckhardti. These species are classified in the family Faujasiidae, part of the stem group of clypeasteroids, with origin in the Campanian (Cretaceous). The records of families Echinarachniidae and Mellitidae (Nieto and García, 2006) are incorrect. These results support the phylogenetic hypothesis on the origin of the order Clypeasteroida proposed by Kroh and Smith (2010).

The correct revision and tracing of the taxonomic information in the paleontological collections allows us to correct catalog numbers of the National Paleontological Collection (IGM) assigned wrongly and published by Durham (1994).

Continuous reviews of the data deposited in biological and paleontological collections are needed in order to study and propose a robust phylogenetic hypothesis for the family Faujasiidae and to update and amend taxonomic information to eliminate mistakes.



To CONACYT scholarship No. 35167 and the EPE fellowship. To Dan Levin (Smithsonian Museum of Natural History) and Violeta Romero (IGL-UNAM) for their help in accessing the collections. To Juan Miguel Contreras for his support with the images. To Josep A. Moreno Bedmar and Jesús Alvarado Ortega for their critical reading of early drafts of the manuscript. To Ryan O. Roney for his English revision.



Agassiz, A., 1872–1874, Revision of the Echini: Memoirs of the Museum of Comparative Zoology, 3, 383–762.

Agassiz, A., 1874, Illustrated catalogue of the Museum of Comparative Zoology, at Harvard College (No. 7): Cambridge, USA, Sever and Francis, Memoirs of the Museum of Comparative Zoology, 3, 1–762.

Agassiz, L., 1841, Monographies d’échinodermes. II Livraison, contenant les Scutelles: Neuchatel, Suisse, Imprimerie de Petitpierre à Neuchatel, 151 p.

Bittner, A., 1892, Über echiniden des Tertiärs von Australien: Sitzungsberichte der kaiserlichen Akademie der Wissenschaften zu Wein (Mathematisch-Naturwissenschafliche Classe), 101, 331–371.

Böse, E., 1906, Sobre algunas faunas terciarias de México: Boletín del Instituto de Geología, 22, 1–96.

Clark, H.L., 1946, Echinoderm fauna of Australia, its composition and its origin: Washington D.C., U.S.A., Carnegie Institution of Washington Publication, 567 p.

Cooke, C.W., 1942, Cenozoic Irregular Echinoids of Eastern United States: Journal of Paleontology, 16, 1–62.

Cooke, C.W., 1953, American Upper Cretaceous Echinoidea, A Shorter Contribution to General Geology: Geological Survey Professional Paper, 254–A, 1–44.

Cotteau, G., 1866, Échinides nouveaux ou peu connus: Revue et Magasin de Zoologie Pure et Appliquée, 2, 262–268.

d’Archiac, V.D., Haime, J., 1853, Descriptions des animaux fossiles du groupe nummulitique de l’Inde. Paris, France, Gide and Baudry. 373 p.

Desor, É., 1858, Synopsis des échinides fossiles: Paris, France, Reinwald, 490 p.

Duncan, P.M., 1889, A revision of the genera and great groups of the Echinoidea: Zoological Journal of the Linnean Society, 23, 1–311.

Durham, J.W., 1950, 1940 E.W. Scripps Cruise to the Gulf of California. Part II, Megascopic paleontology and marine stratigraphy: Geological Society of America, Memoir 43, 1–75.

Durham, J.W., 1955, Classification of clypeasteroid echinoids: University of California Press, 31, 73–197.

Durham, J.W., 1994, Fossil Encope (Echinoidea) from the Pacific coast of southern Mexico: Revista Mexicana de Ciencias Geológicas, 11, 113–116.

Emmons, E., 1858, Report of the North Carolina Geological Survey: Agriculture of the Eastern Counties. Together with Descriptions of the Fossils of the Marl Beds: North Carolina, U.S.A., H.D. Turner, 314 p.

Ferrusquía-Villafranca, I., Ruiz-González, J.E., Torres-Hernández, J.R., Martínez-Hernández, E., Gama-Castro, J., 2016, A Miocene Formation from the Peotillos-Tolentino Graben fill, Western Sierra Madre Oriental at San Luis Potosí, Mexico: Part 1, Geology: Boletín de la Sociedad Geológica Mexicana, 68, 274–282.

Gregory, J.W., 1891, The Maltese fossil echinoids and their evidence of the correlation of the Maltese rocks: Transactions of the Royal Society of Edinburgh, 36, 585–639.

Haeckel, E., 1896, Systematische Phylogenie der wirbellosen Thiere (Invertebrata). Vol. 2. Berlin, Germany, Georg Reimer Verlag, Berlin, 720 p.

Israelsky, M.C., 1924, Notes on some echinoids from the San Rafael and Tuxpan beds of the Tampico Region, Mexico: California Academy of Sciences Proceedings, 12, 137–145.

Kier, P.M., 1962, Revision Of The Cassiduloid Echinoids: Smithsonian Miscellaneus Collections, 144, 1–262.

Kier, P.M., 1982, Rapid evolution in echinoids: Palaeontology, 25, 1–9.

Kier, P.M., Lawson, M.H., 1978, Index of Living and Fossil Echinoids. 1924–1970: Smithsonian Contributions to Paleobiology, 34, 1–182.

Kroh, A., Smith, A.B., 2010, The phylogeny and classification of post-Paleozoic echinoids: Journal of Systematic Palaeontology, 8, 147–212.

Lambert, J., 1905, Notes sur quelques ´Echinides éocéniques de l’Aude et de l’Hérault, in Doncieux, L. (ed.), Catalogue descriptif des fossiles nummulitiques de l’Aude et de l’Hérault: Annales de l’Université de Lyon, Nouvelle Série, I. Sciences, Médecine, 17, 129–164.

Lambert, J., 1936, Quelques nouveaux Échinides fossiles du Crétacé du Mexique: Bulletin de la Société Géologique de France, 5, 3–6.

Lambert, J., Thiéry, P., 1921, Essai de nomenclature raisonnée des Échinides: Charmont, France, Libraire La Ferrière, 607 p.

Leske, N.G., 1778, Jacobi Theodori Klein naturalis dispositio echinodermatum. Accesserunt Lucubratiuncula de aculeis echinorum marinorum et Spicilegium de belemnitis, edita et descriptionibus novisque inventis et synonomis auctorem aucta. Addimenta ad I.T. Klein naturalem dispositionem Echinodermatum. Leipzig, Germany, G.E. Beer, 278 p.

Michelin, H., 1851, Description de quelques nouvelles espèces d’Échinides: Revue et Magasin de Zoologie, 2, 1–5.

MNHM, 2017, Échinodermes fossiles (on line) : Paris, France, Museum National d’Hitoire Naturelle, available in <>, consulted on November 15th, 2017.

Mooi, R., 1987, A cladistic analysis of the sand dollars (Cypeasteroida: Scutellina) and the interpretation of hetherochronic phenomena: Toronto, Canada, University of Toronto, PhD thesis, 208 p.

Mooi, R., 1989, Living and fossil genera of the Clypeasteroida (Echinoidea: Echinodermata): an illustrated key and annotated checklist: Smithsonian Contributions to Zoology, 488, 1–51.

Mortensen, T., 1948, A Monograph of the Echinoidea. IV. 2. Clypeastroida. Clypeastridae, Arachnoididae, Fibulariidae, Laganidae and Scutellidae. Text: Copenhagen, Denmark, Reitzel, 471 p.

Morton, S.G., 1834, Synopsis of the Organic Remains of the Cretaceous Group of the United States: Illustrated by Nineteen Plates. To which is Added an Appendix, Containing a Tabular View of the Tertiary Fossils Hitherto Discovered in North America: Philadelphia, USA, Key & Biddle, 154 p.

Myers, R.L., 1968, Biostratigraphy of the Cárdenas Formation (Upper Cretaceous) San Luis Potosí, Mexico: Paleontología Mexicana, 24,1–89.

Nieto, I., García, P., 2006, Cretaceous echinoids of Mexico, in Vega, F.J., Nyborg, T.G., Perrilliat, M.C., Montellano-Ballesteros, M., Cevallos-Ferriz, S.R.S., Quiroz-Barroso, S.A. (eds.), Studies on Mexican Paleontology: Dordrecht, The Netherlands, Springer, 101–112.

Oppenheim, P., 1915, Die eocänen Invertebraten. Fauna des Kalksteins in Togo im Zusammenhange mit anderen Tertiärablagerungen Afrikas vergleichend betrachtet: Beiträge zur geologischen Erforschung der deutschen Schutzgebiete, 12, 1–26.

Pomel, N.A., 1883, Classification méthodique et genera des échinides vivants et fossiles: Paris, France, Alger A. Jordan. Faculté des Sciences de Paris. PhD thesis, 131 p.

Sánchez-Rodríguez, M.A., 1997, Paleobiogeografía de equinoideos del Cretácico Superior (Maastrichtiano) de Nuevo León, San Luis Potosí y Guerrero: Distrito Federal, México, Universidad Nacional Autónoma de México, Bachelor Thesis, 88 p. + 28 ilustraciones.

Seilacher, A., 1979, Constructional morphology of sand dollars: Paleobiology, 5, 191–221.

Smith, A.B., 1984, Echinoid Palaeobiology. Special Topics In Palaeontology: London, England, George Allen and Unwin, 202 p.

Smith, A.B., Kroh, A., 2011, The Echinoid Directory (on line): London, England, Museum of Natural History, available in <>, consulted on November 15th, 2017.

Smith, A.B., Wright, C.W., 2000, British Cretaceous echinoids. Part 6, Neognathostomata (Cassiduloids): Monographs of the Palaeontological Society, 154, 391–429.

Smith, A.B., Pisani, D., Mackenzie-Dodds, J.A., Stockley, B., Webster, B.L., Littlewood, D.T.J., 2006, Testing the molecular clock: molecular and paleontological estimates of divergence times in the Echinoidea (Echinodermata): Molecular Biology and Evolution, 23, 1832–1851.

Squires, R.L., Demetrion, R.A., 1993, A new species of the clypeasteroid echinoid Astrodapsis from the Miocene Isidro Formation, Baja California Sur, Mexico: Journal of Paleontology, 67, 258–263.

Squires, R.L., Demetrion, R.A., 1994, A new species of the oligopygoid echinoid Haimea from the lower Eocene of Baja California Sur, Mexico: Journal of Paleontology, 68, 846–851.

Wang, C.C., 1984, Fossil Echinodiscus from Taiwan: Bulletin of The Central Geological Survey, 3, 107–115.


Manuscript received: February 15, 2018

Corrected manuscript received: April 26, 2018

Manuscript accepted: May 7, 2018