THE FIRST RECORD OF THE EOSIDERASTREA LÖSER, 2016 (CNIDARIA, SCLERACTINIA) IN THE BRAZILIAN CRETACEOUS

1. THE FIRST RECORD OF THE EOSIDERASTREA LÖSER, 2016 (CNIDARIA, SCLERACTINIA) IN
THE BRAZILIAN CRETACEOUS
V. A. TÁVORA1, *, J. J. DIAS2, and E. J. ANDRADE3
1IG/ Universidade Federal do Pará, Belém/ PA- Brazil
2IGEO/ Universidade Federal do Rio de Janeiro, Rio de Janeiro- RJ- Brazil
3DGEOL/ Universidade Federal de Sergipe, Aracaju- SE, Brazil
* vladimir@ufpa.br
INTRODUCTION
The coral family Siderastraeidae is an important group of extant marine invertebrates that occurs worldwide. Their early
members date from late Valanginian and became diversified during the Early Cretaceous. Eosiderastrea is the most common and
oldest genera, restricted to Cretaceous, with constant occurrence from the Valanginian to Santonian. This study deals with the
first record of Eosiderastrea in the brazilian Cretaceous.
Bender (1961) and Fernandes (1985) only cited the occurrences of coralline bioconstructions in outcrops of the Riachuelo
formation (Aptian- Albian, Sergipe basin) located at Areia Branca city in Sergipe state. After, Mascarenhas (2011) recognized 15
specimens of incrusting colonies belonging to Siderastrea sp. collected at Cafuz 1 section.
Location map of the localities

2. MATERIAL AND METHODS
The analyzed material comprises specimens represented by two fragments of massive colony collected at Cafuz 1 and Rosário 1 sites, near
Areia Branca and Rosário do Catete cities, Sergipe state. The primary calcitic composition of the corals skeleton is not preserved and the
diagnostic morphological features were described with a Leika S6E binocular stereomicroscope, with a precision caliper for obtaining
dimensions. The scarcity of the individuals prevented the lead up of thin sections in both transversal and longitudinal orientation.
The essential terminology and nomenclature, descriptions and classification system used in this research is mainly based on Baron-Szabo
(2002) that comprise a combination of different proposed classifications including Wells (1932), Vaughan and Wells (1943), Wells (1956) and
Cairns (1989). The supplementary remarks was incorporated in specific descriptions if it differs from the family or generic character (Löser,
2016).
The distinction Eosiderastrea species are mainly based on the calicular symmetry and measures of septae (number and cycles) and walls
(thickness).

3. RESULTS
Order SCLERACTINIA Bourne, 1900
Suborder FUNGIINA Verrill, 1865
Superfamily AGARICIICAE Gray, 1847
Family SIDERASTREIDAE Vaughan & Wells, 1943
Genus Eosiderastrea Löser, 2016
Eosiderastrea harrisi (Wells, 1932)
Description: Corallum massive, hemisferical and plocoid to subplocoid colony attaining a diameter of 20 cm or more, with small, tall, asteroid,
elongate and cylindrical coralites bounded by a poorly defined and thin synapticular wall. Calicular outline circular to subcircular, thick and
peripherally equal and depressed with upper margins smooth and little arched. Synapticulae fairly common fused or joined forming a meshwork in
the space between the calices. The septal number vary from 22 to 30 units, generally compact, lamellate, straight, subequal, equally spaced and
slightly elevated, thick in the region of the wall and much thinner toward the center, with distal margins laterally granulated and non-confluent,
arranged in eight systems and three cycles. Septa of older generations (first and second cycles) are fused in the centre of the calice, thicker and
less laminated than of younger generation, that are attached laterally to those of preceding generations. Costae prominent, confluent and thicker
in inner margin than upper margin. Columella poorly defined, small and trabecular, being fused to the inner edges septal. Endotheca, coenosteum
and dissepiments absent.
Eosiderastrea harrisi (Wells, 1932): A,
B general view of the corallum; C, D
detailed view of the calice and septa
(ct- costae, cr- corallite, ca- calice,
cm- columella, s septa).

4. DISCUSSION
The genera Siderastrea belonging to the family Siderastraeidae was recognized and ilustrated by Mascarenhas (2011) in the
Riachuelo Formation. However the arrangement of septal elements and absence of costae are not typical of Siderastrea but of
Eosiderastrea (Löser, 2016a, b). The distinction Eosiderastrea species are mainly based on the calicular symmetry and measures
of septae (number and cycles) and walls (thickness). The morphology of the colony, septal apparatus, costae and calicular
diameter dimensions are diagnostic traits of E. harrisi (Wells, 1932) in studied specimen.
E. harrisi differs of the E. cotteaui (Orbigny, 1850) and E. crassicostata Moricowa and Masse, 1998 in the number of septal
systems. With E. stefani Löser, 2016 is distinct in the arrangement and calicular dimensions. The main differences between E.
harrisi and E. grandipora (Orbigny, 1850) are the corallum dimensions and the outline and number of costae. When proposed E.
harrisi still assigned to the genus Diploastrea, Wells (1932) pointed out that D. heliopora Lamarck, 1816 and D. crassolamellosa
Duncan, 1863 are distinct from its new species in the larger corallites and with more septa.
The genus diversified during Hauterivian to Albian, reaching highest diversity in Cenomanian; it is absent in the early Barremian,
late Albian, Turonian and Coniacian, probably due to a lack of adequate sampling. Eosiderastrea is worldwide distributed,
specially abundant in Tethys, except during the Albian when it was more abundant in the Western Atlantic.

5. CONCLUSIONS
The first record of the genus Eosiderastrea in the Sergipe basin:
1- Attest that the coral family Siderastraeidae was an important group of extant marine invertebrates that became diversified
during the Early Cretaceous and Eosiderastrea was the most common and oldest genera, restricted to Cretaceous,
2- confirms a Tethyan affinity of the paleofaune in the Albian brazilian deposits, when this genus was specially abundant in the
Western Atlantic and reach worldwide distribution;
3- suggest the presence of marine conditions with considerably well-developed oxygen minimum zone as attested by
microfaunal evidences.