A Jurassic (Bathonian-Callovian) Daghanirhynchia Brachiopod Fauna from Jordan

Brachiopoda. Systematics. Wadi Zarqa. Ethiopian Province. Middle Jurassic.


INTRODUCTION
According to Kiessling et al. (2011) the Jurassic Ethiopian Province includes Tunisia, the Levant, Arabia and much of East Africa, but excludes Tanzania and India. They consider that the special status of India and Tanzania is possibly due to latitudinal gradients in faunal composition. In this paper we believe that the Ethiopian Province consists of today's Arabian Peninsula, Jordan, the Sinai Peninsula and other neighboring basins, the Horn of Africa, parts of the eastern Mediterranean coast, and northeastern Africa. During the Middle Jurassic it was part of the southern Tethys with a characteristic faunal content. Strata of the Ethiopian Province were studied intensely during petroleum exploration after the First World War; however, primary attention was paid to structural geology and sedimentology. Italian and British geologists made large fossil collections that were described piecemeal by paleontologists (e.g. Weir 1925Weir , 1929Hudson, 1958;Jaboli, 1959;Ficcarelli, 1968). Special attention was paid to the ammonite and foraminiferal faunas because of their stratigraphical value. Referring to the brachiopod faunal assemblages, Weir (1925Weir ( , 1929 and Muir-Wood (1935, 1936 described the brachiopod fauna from Somalia; Weir (1929) from Kenya, Cooper (1983Cooper ( , 1989 from Saudi Arabia, andFeldman (1986, 1987), Feldman et al. (1991Feldman et al. ( , 2012a, and Hegab (1989Hegab ( , 1992 from Sinai; Feldman et al. (2001) and Krawczynski andWilson (2011) from Israel, andFeldman et al. (2012b) from Jordan. A more detailed stratigraphical summary of the Jurassic strata in Somalia (formerly British Somaliland) can be found in Weir (1929) and Muir-Wood (1935). Cooper (1989) described brachiopods from Saudi Arabia that were collected from 1125.6m of Jurassic strata. These strata are comprised of seven formations, for a more detailed description of these formations see Cooper (1989) and Sharief (et al., 1991). Overall correlation of the faunas among these regions on a larger scale is, with few exceptions, still lacking. This paper is one of a series dealing with fossil finds from Jordan and their correlation with various regions within the Ethiopian Province.
The genus Daghanirhynchia was first established by Muir-Wood (1935). However, its first species were described by Weir (1925) and subsequently Cooper (1989) described additional species. Cooper (1989) and Shi and Grant (1993) discussed the inclusion of taxa assigned to other genera into Daghanirhynchia. In a preliminary work, Feldman et al. (2012b, figs. 1-3) identified a new species in the Arda section of Jordan. Two new species of Daghanirhynchia are described herein and the paleobiogeographical relationship between the Daghanirhynchia faunas from the Ethiopian Province is noted. The genus occurs in the Sinai Peninsula at Gebel Engabashi (Feldman, et al., 2012a) and Saudi Arabia (Cooper, 1989) however this distribution is a bit puzzling since it is apparently missing from correlative strata in the Negev. This paper presents new data that will add to our knowledge of the distribution of the genus within the Jurassic Ethiopian Province, enhance the genus as a biostratigraphical tool and increase our knowledge of the genus within the Tethyan Faunal Realm as a whole, except for the comparison with specimens from Asia which were omitted due to lack of material.

GEOLOGICAL SETTING
The material studied herein include two stratigraphic sections, the Arda section and the Tel el Dhahab section, both from Wadi Zarqa (Figs. 1; 2) in northwestern Jordan almost due north of the Dead Sea. Wadi Zarqa was first recognized by Wetzstein (1859) and further discussed by Libbey and Hoskins (1905). The base of the Jurassic in northwestern Jordan lies on Triassic siliciclastic sediments (Bender, 1974). The Jurassic in northwestern Jordan is subdivided into seven formations: Hihi, Nimr, Silal, Dhahab, Ramla, Hamam, and Mughanniyya (Khalil and Muneizel, 1992). Brachiopod-bearing levels are found in the Hamam Formation (Bathonian) and Mughanniyya Formation (Callovian) (Fig. 3). The ages of the formations under study are based mainly on bivalves, gastropods and corals since ammonites are relatively scarce in the region (Ahmad, 2002).
The mixed carbonate and siliciclastic Hamam Formation was defined by Khalil and Muneizel (1992) from its type area along Wadi Hamam. It consists of friable sandstones, marls, and clayey silts. Its base is marked by the first appearance of fossiliferous limestone beds, whereas the top is marked by the overlying Mughhanniyya Formation.
The Mughanniyya Formation is composed of alternating claystones, siltstones, and marly limestone beds with minor dolomite, dolomitic limestone, and coquinas; it represents the upper part of the Jurassic sequence in Jordan cropping out consistently below the overlying Kurnub Sandstone Group.

STRATIGRAPHY AND CORRELATION
The genus Daghanirhynchia is easy to recognize due to its external morphology and rib structure. It is subtriangular to subpentagonal, subglobose, dorsibiconvex, and often with large and curved ventral beak. The shell is uniplicate with a distinct dorsal fold. The costae are coarse and angular and do not bifurcate. There are fine radial striae on the slopes of the costae. Its taxa are very useful index fossils for Middle Jurassic strata from the Ethiopian Province; however, most species seem to be A Jurassic Daghanirhynchia (brachiopod) fauna from Jordan 3 geographically restricted. In general, it can be said that specimens from Somalia and Ethiopia are larger in size than in other parts of the Ethiopian Province and shell size increases in stratigraphically younger specimens. Figure 4 shows an overview of the stratigraphical and geographical distribution of Daghanirhynchia species in the Ethiopian Province. Our data are taken from Weir (1925Weir ( , 1929, Muir-Wood (1935), Hudson (1958), Jaboli (1959), Dubar (1967), Cooper (1989), Shi and Grant (1993), Howarth and Morris (1998), Ahmad (1998Ahmad ( , 2000Ahmad ( , 2002Ahmad ( , 2003, Feldman et al. (2001Feldman et al. ( , 2012b, the PBDB (Paleobiology Database; http:// www.paleodb.org), and our own observations. According to Kiessling et al. (2011), India, Tanzania, and China are not included in the Ethiopian Province. However, it must be noted that Muir-Wood (1937) reported Daghanirhynchia from India. We believe in the accuracy of her assignment since she had erected the genus. At present, the occurrence of Daghanirhynchia in India is the only appearance of the genus outside the Ethiopian Province. During the Jurassic India was still attached to Africa (Gondwana) and was part of the Ethiopian Province; it began drifting toward Asia only in the Cretaceous.

MATERIAL AND METHODS
All 213 specimens studied are preserved as articulated shells. To study the internal morphology we used serial sections and computer tomographical (CT) scans of nine specimens. The latter was only suitable for the type species, Daghanirhynchia daghaniensis, from Ethiopia because the shells were silicified and the composition of shell and sediment matrix allowed sufficient contrast for adequate images. Computer tomographical data were taken with a Phoenix / X-Ray with a 180kV highpower nanofocus tube and a tungsten target using a scanning distance between 10 and 35μm. Serial sections were prepared using a Struers Discoplan-TS grinding machine with slice-spacing of 50 or 100μm starting from apex in an anterior direction perpendicular to commissural plane. Grinding surfaces were subsequently digitized using a digital camera (Canon 300D). Threedimensional reconstruction methods are those of Sutton et al. (2001Sutton et al. ( , 2005, using the custom SPIERS software suite for registration, virtual preparation, and interactive visualization. The photos of the grinding surfaces were subsequently manually aligned with SPIERSalign. In a second step, photos and CT (Computed Tomography) images were edited using different masks in SPIERSedit. The obtained 3D images were copied out of SPIERSview. Drawings of the peels were made with the help of a camera lucida. Measurements were taken with a digital caliper and rounded to 0.1mm or using free ImageJ 1.43μ software. Specimens were coated with ammonium chloride or magnesium oxide prior to photographing. The systematics follows the revised Treatise on Invertebrate Palaeontology (Part H, no. 4); taxonomic assignments follow (Manceñido et al., 2002). Specimens are in repository at the American Museum of Natural History, New York, the Geological Survey of Israel, Jerusalem, the Natural History Museum, London, The Museum für Naturkunde, Berlin, and the United States National Museum of Natural History/Smithsonian Institution, Washington.

Institutional abbreviations
AMNH: American Museum of Natural History, New York, USA; MB.B.: Museum für Naturkunde Berlin, Germany; GSI: Geological Survey of Israel, Jerusalem, Israel; NHM: Natural History Museum, London, UK; USNM: United States National Museum of Natural History/Smithsonian Institution, Washington DC, USA.

Species included
Daghanirhynchia daghaniensis Muir- Wood, 1935; ?Rhynchonella hadramautensis Stefanini, 1925; Somalirhynchia subversabilis Weir, 1925 Dubar, 1967;Daghanirhynchia angulocostata Cooper, 1989; Daghanirhynchia sulcata Cooper, 1989; A B  Discussion. Species of Daghanirhynchia are mostly defined based on external morphology rather than on internal features. Serial sections of D. daghaniensis and D. angulocostata are given in Muir- Wood (1935) and Cooper (1989). In an earlier work (Feldman et al., 2012b) we showed serial sections of D. susanae which are re-figured herein. Serial sections of D. macfadyeni from the Muir-Wood collection housed in the NHM were taken and a CT scan of D. daghaniensis from Ethiopia was prepared. Owing to strong homoeomorphy we recommend the erection of new taxa based on internal and external shell morphology. For comparison the diagnoses, stratigraphical and geographical distribution of all Daghanirhynchia species are given, but further description is omitted due to lack of (internal) information. We could not study the specimens from Jaboli (1959), Rousselle (1965), and Dubar (1967), therefore, species assignment to Daghanirhynchia is noted with a question mark; these were noted by Cooper (1989) and Shi and Grant (1993). Diagnosis. Daghanirhynchia with 11 to 15 costae on each shell, 3 to 4 in the sulcus and 4 to 5 on the fold, thick and divergent dental plates, a long and thick dorsal median septum, raduliform crura, wedge-like dental plates.

Daghanirhynchia rawyaensis
Description. Shells medium-sized subpentagonal, dorsibiconvex with maximum width at midlength. Apical angle is 99 degrees. Eleven to 15 costae on each valve, of which 3 to 4 are in the sulcus and 4 to 5 on the fold. Costae simple and angular in cross-section. Fold and sulcus originating at midlength of shell. Sulcus tongue high, reaching maximum curvature of dorsal valve, and with rounded to rarely straight anterior margin. Beak erect and incurved in adult specimens. Dorsal interarea concealed.
Interior of ventral valve. Moderate development of secondary shell material in the apical region slightly filling the umbonal cavities (see Fig. 5C). Dental plates thick, divergent, and wedge-like posteriorly leading into massive teeth that are oriented in a dorsal direction. Denticular cavities rounded in cross-section (Figs. 5C; 7).
Discussion. Daghanirhynchia rawyaensis differs from D. jordanica in 1 to 2 costae less on fold and sulcus, gently  F e l d m a n e t a l .   G e o l o g i c a A c t a , 1 2 ( 1 ) , 1 -1 8 ( 2 0 1 4  A Jurassic Daghanirhynchia (brachiopod) fauna from Jordan 9 more development of secondary shell material, thick and divergent dental plates, and a longer and thick dorsal median septum.
Daghanirhynchia rawyaensis n. sp. has 6 costae less on each valve than D. daghaniensis; the sulcus shows 1 rib less and the fold 1 to 2 costae less than in the type species. Daghanirhynchia daghaniensis has a short and fine dorsal median septum, whereas D. rawyaensis has a long and thick dorsal median septum. The crura of the type species extends further in a ventral direction than the crura of D. rawyaensis.
Daghanirhynchia macfadyeni differs from D. rawyaensis n. sp. By having 3 to 7 more costae on each shell, but the amount of costae in sulcus and fold is the same, less secondary shell material, a subtriangular outline, thin and parallel dental plates, and a shorter dorsal median septum.
The shells of Daghanirhynchia susanae are smaller and have less secondary shell material, 1 to 2 costae less on fold and sulcus, thin dental plates, a short dorsal median septum, and longer crura than D. rawyaensis.
?Daghanirhynchia triangulata has a subriangular outline compared to D. rawyaensis. Daghanirhynchia angulocostata differs from D. rawyaensis in that there are 1 to 3 more costae on each shell and a thin dorsal median septum is present. Diagnosis. Daghanirhynchia with 14 to 16 costae on each shell, 4 to 5 in sulcus and 5 on fold. Hardly any development of secondary shell material, thin and parallel dental plates, and a high and blade-like dorsal median septum. Septalial plates are narrow and parallel to one another.
Description. Shells medium-sized, subpentagonal, gently dorsibiconvex with maximum width at midlength of shell or anterior to it. Apical angle is 98 degrees. Shells covered by 14 to 16 simple and rounded to angular costae, of which are 4 to 5 in the sulcus and 5 on the fold. Sulcus and fold originating at midlength of shell. Sulcal tongue almost reaching maximum curvature of ventral valve and with rounded anterior margin. Ventral umbo moderately long and suberect. Dorsal interarea concealed.
Interior of ventral valve. Hardly any development of secondary shell material. Umbonal cavities free, ventral median septum lacking. Dental plates short, thin, and parallel to each other, leading into short and knob-like teeth that project dorsally.
Interior of dorsal valve. No development of secondary shell material. Dorsal median septum short and bladelike. Septalium weakly developed, hardly recognizable. Septalial plates narrow and parallel to one another. Dental sockets rounded in cross-section. Inner socket ridges show tendency to curve over dental sockets. Hinge plate arched leading into raduliform, slightly curved ventrally crura.
Discussion. Daghanirhynchia jordanica n. sp. has 3 to 5 costae less than the type species D. daghaniensis, but the amount of costae on fold and sulcus is the same. Furthermore, D. jordanica has hardly any development of secondary shell material, parallel and thin dental plates, a higher dorsal median septum, narrow and parallel septalial plates, and gently ventrally curved crura. Daghanirhynchia daghaniensis shows stronger development of secondary shell material, divergent dental plates, a lower dorsal median septum and septalial plates that are oriented almost parallel to each other. Daghanirhynchia jordanica has 2 to 4 less costae on each shell than D. macfadyeni, a subpentagonal outline, a higher dorsal median septum, and parallel septalial plates. Daghanirhynchia jordanica differs from D. susanae (see Fig. 11) in that it possesses 1 to 2 more costae, less secondary shell material, parallel dental plates, a higher dorsal median septum, and shorter crura. Daghanirhynchia angulocostata has 1 less costa on the sulcus and 1 more costa on the fold than D. jordanica. ?Daghanirhynchia triangulata shows a subtriangular outline and 1 to 2 costae less on fold and sulcus than D. jordanica.  F e l d m a n e t a l .   G e o l o g i c a A c t a , 1 2 ( 1 ) , 1 -1 8 ( 2 0 1 4  Type horizon and type locality. Bed φ.227, Daghani section, Somalia (detailed description is given in Muir- Wood, 1935,  Diagnosis. Dorsibiconvex Daghanirhynchia with subtriangular to subpentagonal outline and with moderate development of secondary shell material in the apical region of both valves. Costae coarse and subangular, 17 to 21 on each valve, with 3 to 6 on fold and 2 to 5 in the sulcus. Dental plates slightly divergent and dorsal median septum short. Septalium lacking or imbedded into secondary shell material.

Daghanirhynchia daghaniensis
Description. Shells medium-sized, subtrigonal to subpentagonal, and dorsibiconvex. Ventral valve posteriorly convex with maximum convexity at midvalve to anterior. Apical angle is 95 degrees. Numerous rounded costae, 17 to 21 on each valve, 3 to 6 on fold, 2 to 5 in sulcus. Sulcus well developed, broad, steep, with flattened bottom and beginning at posterior 1/3 to 1/2 part of shell. Sulcus tongue high, trapezoidal. Fold raised significantly over flanks, broad, pronounced, rounded at top, and starting at posterior 1/3 to 1/2 part of shell.
Interior of ventral valve. Hardly any development of secondary shell material in the apical region. Ventral umbonal cavities small and narrow. Dental plates slightly divergent toward ventral valve floor, splitting away from floor just at hinge line, and leading into short, massive teeth rectangular in cross-section. Crenulation was not observed.
Interior of dorsal valve. Hardly any development of secondary shell material in the apical region. Dorsal median septum short and supporting hinge plates only at very posterior of apical cavity; it is preserved as a reduced ridge extending for about 1/4 of valve length in an anterior direction. Septalium lacking, septalial plates very short. Hinge plates broad, clearly separated, slightly inclined or arched ventrally and tapering anteriorly. Inner socket ridges low, well demarcated from hinge plates. Crural bases not well formed, leading into raduliform crura that extend about 1/5 of dorsal valve length almost protruding along commissural plane and only slightly incurved ventrally at distal ends. Crura arise from prolongations of hinge plate, relatively wide and somewhat similar to ciliform at preliminary parts in cross-section.
Stratigraphical and geographical occurrence. Bathonian to ?Oxfordian (Middle to ?lower Upper Jurassic); Yemen, Jordan, Saudi Arabia, Somalia, Ethiopia. Muir-Wood, 1935 differs from all Daghanirhynchia taxa from Jordan in its larger shells and more numerous costae.

Discussion. Daghanirhynchia daghaniensis
Daghanirhynchia susanae Feldman et al. (2012b) differs from D. daghaniensis in smaller shells, 5 ribs less on each valve, only 2 to 3 costae on fold and sulcus, less secondary shell material, parallel septalial plates, and long crura that are slightly curved ventrally. Muir-Wood, 1935 has almost the same number of costae, but less secondary shell material, a subtriangular outline, thin dental plates, a small and short septalium, and crura extending less distance in a ventral direction than in D. daghaniensis.

Daghanirhynchia macfadyeni
?Daghanirhynchia triangulata Cooper, 1989 has 1 to 3 less costae on each shell, less secondary shell material in the apical region, and a subtriangular outline. Daghanirhynchia angulocostata Cooper, 1989 has 3 to 5 less costae on each shell, a longer dorsal median septum and a small septalium.
A morphological comparison of Daghanirhynchia taxa from Jordan and the type species is given in Table 1.   o l o g i c a A c t a , 1 2 ( 1 ) , 1 -1 8 ( 2 0 1 4  Emended diagnosis. Daghanirhynchia with subtrigonal shell outline, strongly dorsibiconvex with low median fold and broad shallow sulcus, ornamentation consists of 18 strong and angular costae, with 4 to 5 on fold and 3 to 4 in sulcus, and anterior commissure significantly thickened in adult specimens. After Muir- Wood (1935, 88).

Daghanirhynchia macfadyeni
Description. Shells medium to large, subtriangular and strongly dorsibiconvex. Ventral valve convex posteriorly, medially flattened. Slightly longer than wide with maximum width at midlength. Apical angle is 94 degrees. Fold low, sulcus broad and shallow at anterior margin. Eighteen costae on each valve, 4 to 5 in fold, 3 to 4 on sulcus. Costae coarse, prominent angular and curved on flanks. Sulcus tongue broad and rectangular. Ventral umbo long and strongly incurved in adult specimens. Interareas narrow, flattened, and smooth. Anterior commissure deflected toward dorsal valve, whereas the lateral commissure is slightly curved. Beak ridges rounded.
Interior of ventral valve. Hardly any development of secondary shell material in the apical region. Umbonal cavities free. Ventral median septum lacking. Dental plates thin and parallel to each other, leading into coarse and knob-like teeth that are pointing in a dorsal direction. Denticular cavities rounded in cross-section. Interior of dorsal valve. Hardly any development of secondary shell material. Dorsal median septum short and thin. Septalium small and short, only developed in the posterior part of the shell with septalial plates that are oriented almost parallel to each other. Dental sockets rounded in cross-section. Inner socket ridges straight. Hinge plate very short, divided, and leading into short raduliform crura that do not extend far ventrally.
Discussion. Daghanirhynchia susanae differs from D. macfadyeni in its smaller size, slightly greater development of secondary shell material, a subpentagonal outline, divergent dental plates, parallel septalial plates, and longer crura that are extending further in an anterior direction.
?Daghanirhynchia triangulata has 1 to 2 costae less on shells and on fold and sulcus and a narrower triangular outline than D. macfadyeni.
Daghanirhynchia angulocostata has two less costae than D. macfadeyni, a subpentagonal outline, and a longer dorsal median septum.
Description. Shells large, wide, and subpentagonal in outline with maximum width shifted toward the anterior margin. Anterior margin broadly rounded, uniplicate. Apical angle is 99 degrees. Fourteen to 16 costae on each shell, 3 to 5 on sulcus and 4 to 6 on fold. Sulcus starts slightly posterior to midvalve and widens rapidly. Sulcal tongue moderately long. Flanks bounding the sulcus narrow and become flat to slightly convex. Dorsal valve fairly strongly convex, median region swollen. Fold starting slightly posterior of midvalve elevating moderately, slowly widening at the anterior margin. Ventral beak narrow and suberect. Foramen large and elliptically elongated. Deltidial plates disjunct. Umbonal region slightly swollen.
Interior of ventral valve. Unknown.
Interior of dorsal valve. Septalium small. Dorsal median septum extends anteriorly about 1/3 of valve length. The remaining features have not been studied due to the paucity of material.
Discussion. Daghanirhynchia angulocostata differs from D. susanae in that is has 1 to 2 more costae on fold and sulcus and larger shells.

Diagnosis. As in
Description: Shells small to medium-sized, subpentagonal, dorsibiconvex with maximum width at about midlength. Apical angle is 96 degrees. Costae strong, angular, and coarse, numbering 12 to 16 on each shell, 2 to 3 in sulcus and 3 on fold. Fold and sulcus originating anterior to umbonal region of shell. Sulcus tongue high, mostly reaching to maximum curvature of dorsal valve, and with rounded to straight anterior margin. Ventral beak suberect to erect. Beak ridges rounded, strongly uniplicate anterior commissure, linguiform extension moderate, anterior margins end abruptly and a slightly stubby. Foramen small with disjunct deltidial plates.
Interior of ventral valve. Little development of secondary shell material, slightly filling the umbonal cavities. Ventral median septum lacking. Dental plates short and gently divergent leading into short and bulbous teeth that extend dorsally. Denticular cavities rounded and short.
Interior of dorsal valve. Little development of secondary shell material in apical region. Dorsal median septum short, but posteriorly imbedded into secondary shell material. Septalium imbedded or lacking, septalial plates parallel to each other. Dental sockets imbedded into secondary shell material. Hinge plates horizontal and thick. Crura slightly curved ventrally but extending far anteriorly.
Discussion. Daghanirhynchia susanae differs from ?D. triangulata in its smaller shell size, a subpentagonal outline and 2 to 4 less costae on the shell.
Holotype. Articulated shell housed at the USNM under the repository number USNM 380246; length 23.7mm, width 20.6mm, thickness 20.0mm. Remark: The shell is laterally broken, and width gives the measurement of the actual fossil specimen and not of the reconstructed original width. D. rawyaensis n. sp.
Description. Triangular shells anteriorly rounded and narrow with maximum width located at the anterior margin. Gently dorsibiconvex. Apical angle is acute. Lateral commissure straight, anterior commissure strongly uniplicate. Ventral valve slightly swollen medially. Sixteen to 18 costae on each shell, 2 to 3 on sulcus, 3 to 4 costae on fold. Sulcus originating in umbonal region occupying nearly half the width, depressed below flanks throughout, strongly so on anterior half. Fold narrow, moderately elevated above flanks, and originating posterior to midvalve. Ventral beak fairly long and suberect. Foramen large. Deltidial plates narrow and disjunct.
Interior of ventral and dorsal valve. Unknown due to paucity of material.
The comparison of the Daghanirhynchia fauna from Jordan with the Daghanirhynchia fauna from different regions within the Ethiopian Province indicate that the maximum diversity of this genus occurs in the center of the Province (today's Jordan, Saudi Arabia, and Somalia).