Sula brandi, Stucchi & Varas-Malca & Urbina-Schmitt, 2016
|
publication ID |
https://doi.org/ 10.4202/app.00170.2015 |
|
publication LSID |
lsid:zoobank.org:pub:12E70E13-D7F9-43BB-A388-6A93FF0E4A52 |
|
persistent identifier |
https://treatment.plazi.org/id/B338FEDC-FDB1-4C17-88DB-628776BCA613 |
|
taxon LSID |
lsid:zoobank.org:act:B338FEDC-FDB1-4C17-88DB-628776BCA613 |
|
treatment provided by |
Felipe |
|
scientific name |
Sula brandi |
| status |
sp. nov. |
Sula brandi sp. nov.
Fig. 2.
ZooBank LSID: urn:lsid:zoobank.org:act:B338FEDC-FDB1-4C17-88DB-628776BCA613
Etymology: In honor to Leonard Brand (Loma Linda University, USA) for his important contributions to Peruvian vertebrate paleontology, and to the understanding of the geology, stratigraphy, and taphonomic processes of the Pisco Formation.
Holotype: MUSM 2497 ; neurocranium lacking interorbital septum, lacrimals, palatines, pterygoids, jugals, quadrates, and right quadratojugal. Proximal portion of the beak, including most of the right dentary and angular.
Type locality: MUSM 2497 was collected from the Cerro Colorado locality (CCO), Pisco Formation, ~ 23 km west of Ocucaje District, Ica, Peru ( Fig. 1A View Fig ). Coordinates: 14°21’37.90” S, 75°53’17.90” W. The specimen (field number A3 of Bianucci et al. 2015) was found 1–2 km southwest of Cerro Colorado (Colorado hill), between the Wari and Paracas marker beds of its lower allomember (sensu Di Celma et al. 2015). The level from which the sulids were recovered (about 60 m of the stratigraphic column) is the second most fossiliferous in terms of quantity and species diversity, having produced more than 50 specimens, among them osteichthyans, elasmobranchs (myliobatids, Carcharocles , Cosmopolitodus ), long-snouted crocodylians, delphinidans (the pontoporiid Brachydelphis , indeterminate delphinidans), ziphiids ( Messapicetus ), balaenopteroideans, cetotheriids, and physeteroideans (cf. Acrophyseter ) (see Bianucci et al. 2015).
Type horizon: The age of this locality has been estimated according to the presence of the arcid bivalve Anadara sechurana in late Middle Miocene (ca. 12–13 Ma; Lambert et al. 2010). However, due to the occurrence of early Late Miocene diatoms Denticulopsis hudstedtii and Lythodesmium reynoldsii (9.9–8.9 Ma, Tortonian; Barron 2003) in the referred level, the age is younger than previously thought (see Di Celma et al. 2015). Thus, it is correlated with El Jahuay level (9.95 Ma; Muizon and Bellon 1986) and Montemar Norte (about 10 Ma; Stucchi 2007) in the Sacaco area, and possibly with Laguna Seca locality in the Ocucaje area ( Stucchi et al. 2015).
Diagnosis.— Sula with braincase length similar to those of medium-sized boobies S. variegata and S. leucogaster but flattened, being the flattest among sulids; wide naso-frontal hinge, greater laterofacial angle, smaller cerebellar dome, and narrow sagittal crest. Shallow salt gland fossae and shallow postorbital fossae, as occurs in Morus and Papasula , but in contrast to the deep condition found in all other Sula species.
Measurements.—See SOM 1 (Supplementary Online Material available at http://app.pan.pl/SOM/app61-Stucchi_etal_ SOM.pdf).
Description.—In lateral view ( Fig. 2A) the length of the braincase fits well within the range of medium-sized boobies (SOM 1). The anterior region of MUSM 2497 has slightly pronounced supraorbital ridges above the fused frontals, as well as a straight dorsal profile, as it occurs in most species of Sula (note that S. variegata has a slightly domed profile, see Stucchi 2003, 2013). The middle region (parietal, squamosal and laterosphenoid) of MUSM 2497 has the same shape and disposition of Sula , but with a noticeable dorso-ventral flattening (SOM 1: measurement 3). Indeed, MUSM 2497 shows the most dorsoventrally compressed skull among sulids (SOM 1: proportion 6). In the posterior region, there is a large sagittal crest and a shorter and compressed prominentia cerebelaris (supraoccipital) under the posterior projection of the sagittal crest. However, it makes a more acute angle with respect to the horizontal plane.
In caudal (occipital) view ( Fig. 2B), the flattening of the braincase is better appreciated. The whole region is proportionally wider than higher (SOM 1: proportion 6), differing from other sulids. The height at the vertical axis of the supraoccipital (between the superior border of the foramen magnum and the sagittal crest) represents 60% that of S. variegata . Additionally, the medial parasphenoid processes are more laterally placed than those of recent species.
In dorsal view ( Fig. 2C), the face width of MUSM 2497 is wider than those of medium-sized boobies. This is seen in both the breadth at the preorbital skull roof and the width of the naso-frontal hinge. The width is greater than those of S. variegata , S. leucogaster and S. sula , but lies within the range of S. nebouxii (SOM 1: measurement 5). The breadth is greater and reaches the range of large-sized boobies (SOM 1: measurement 6). Therefore, the angle formed by the sagittal axis and the lateral margin of the frontal (latero-facial angle) is 10° in MUSM 2497, which contrasts with the angle reached by medium-sized boobies and S. granti (20° and 18°; Fig. 2C). The middle region exhibits a narrower and longer sagittal crest in comparison to modern species of Sula , except for S. leucogaster . In the posterior region, MUSM 2497 has a rounded supraoccipital, which projects posteriorly to the paroccipital processes of the exoccipitals. In other species of Sula , the supraoccipital is triangular and projects more posteriorly or is at the same level of the paroccipital processes. Both latter characters are also distinguished in other specimens from the Pisco Formation, for instance MUSM 249 (Aguada de Lomas locality, 8.0–8.8 Ma), MUSM 309 and 202 (Montemar locality, 8.70–6.45 Ma) and MUSM 361 (Sacaco Sur locality, 6.59–5.93 Ma), as well as in Ramphastosula ( Stucchi and Urbina 2004) .
In ventral view ( Fig. 2D), the otic region, the articular with the quadrate, the basioccipital and medial parasphenoidal processes resemble those of living Sula . Likewise, the salt gland fossae and postorbital fossae are slightly shallower. The mandible is the same size and shape as those of medium-sized boobies ( Fig. 2E).
Remarks.—MUSM 2497 has the typical cone-shaped skull of extant boobies, although it is more flattened and has wider nasofrontal hinge. Thus, we infer a similar feeding ecology for this species. The sole character considered primitive is the shallow depth of the salt gland fossae and postorbital fossae which are both found in Morus (e.g., USNM 612654) and Papasula (e.g., USNM 560682), as well as inmature individuals of Sula ( Stucchi 2013) . Indeed, the derived condition is seen in adult Sula , which is more in line with their early divergence (23 Ma) from other sulids according to Friesen and Anderson 1997).
Stratigraphic and geographic range.—Tortonian, Pisco depositional sequence, Pisco Formation, South-Central Peru.
Sula figueroae sp. nov.
Fig. 3 View Fig .
ZooBank LSID: urn:lsid:zoobank.org:act:F968A99A-AAF4-4066-B653 B68E1B3E8319
Etymology: In honor to Judith Figueroa (Asociación para la Investigación y Conservación de la Biodiversidad, Peru), for her valuable contributions to the knowledge of the natural history of Peruvian seabirds. Type material: Holotype: MUSM 2501; nearly complete, well-preserved cranium and mandible lacking pterygoids and right lacrimal; one partial thoracic vertebra (? 19–21), three free cervical vertebrae (? 3–7), left scapula, right and partial left humeri, partial right and left ulnae, partial left radius, left carpometacarpus, pelvis without pubis, and partial tarsometatarsi. Paratype: MUSM 2502; associated furcula and sternum, coracoids, scapulae, humeri, distal fragments of ulnae, radius shaft, proximal fragment of left carpometacarpus, partial right carpometacarpus, right and distal fragment of left femora, right tibiotarsus, and right tarsometatarsus.
Type locality: MUSM 2501 and MUSM 2502 (A1 and A2 field numbers, respectively, of Bianucci et al. 2015) were both collected in Cerro Colorado locality, close to Sula brandi ( Fig. 1A View Fig ) . MUSM 2501 coordinates: 14°21’47.30” S, 75°53’0.40” W, 596 masl GoogleMaps . MUSM 2502 coordinates: 14°21’32.70” S, 75°53’21.90” W, 632 masl GoogleMaps .
Type horizon: The same stratigraphic level as Sula brandi ; early Late Miocene (Tortonian).
Diagnosis.— Sula having similar dimensions to the large-sized boobies S. dactylatra and S. tasmani , but with a more robust and much shorter humerus.
Measurements.—See SOM 1–3.
Description.— Skull and mandible: In lateral view ( Fig. 3A View Fig 1 View Fig ), the rostrum is approximately 50% larger than the braincase, which corresponds to the range of all known Sula , although S. sula shows a shorter rostrum (SOM 1: measurement 1). The length of MUSM 2501 is similar to that of S. tasmani , S. nebouxii , the largest specimens of S. dactylatra (sensu Tets et al. 1988), and possibly S. granti . The mandible has the same shape and proportions as those of extant species. The braincase length lies in the same range of large-sized boobies, but is shorter than that of S. tasmani (SOM 1: measurement 2). The anterior region of MUSM 2501 has slightly pronounced supraorbital edges above the fused frontals, a slightly domed skull roof, rather smaller than that of S. variegata (see Stucchi 2003, 2013). Posterior and middle regions of the braincase are slightly flattened compared with other species of Sula (SOM 1: proportion 3). Paroccipital processes of exoccipitals are lower with respect to the horizontal plane as in MUSM 220 (see Stucchi 2003). The width of the skull at the postorbital processes in dorsal view ( Fig. 3A View Fig 4 View Fig ) is proportionally similar to those of the more robust specimens of large-sized boobies, but with a larger postorbital process (SOM 1: measurement 8). A laterally narrow skull is observed in caudal view ( Fig. 3A View Fig 2), which is more evident in its constricted foramen magnum (SOM 1: proportion 4). Shallow salt gland fossae and postorbital fossae, as observed in Morus and Papasula , differing from the deep condition seen in Sula .
Postcranium: The humerus ( Fig. 3B View Fig 5 –B 7) is similar to that of extant species of Sula (see Tets et al. 1988; Stucchi 2003) and S. magna , but more robust (SOM 2). The humerus length of both MUSM 2501 and 2502 falls within the range for S. nebouxii , their proximal width approaches those of S. dactylatra and S. tasmani , and their distal and mid-shaft maximum width are greater than that of S. tasmani . In lateral view ( Fig. 3B View Fig 6), a deformity (healed injury) is observed in the right humerus of MUSM 2502. The proximal width of the ulna is also wider in relation to the distal width of the humerus. The remaining postcranial elements share a similar morphology with the other species of Sula as Warheit (1992) and Stucchi (2003) have pointed out. Some details could be observed when comparing S. figueroae with S. variegata in Stucchi (2011). Moreover, their proportions notably correspond to different species. Thus, carpometacarpus and tibiotarsus are similar in length to that of S. tasmani , whereas the tarsometatarsus is proportionally closer to S. dactylatra . The femur matches the range of those of indeterminate Sula individuals (see Stucchi 2003), which is larger than those of both S. dactylatra and S. tasmani (SOM 3). In addition, the sternum, pelvis and synsacrum reach the dimensions and proportions of large-sized boobies (including the Sula spp. group), wider than those of medium-sized boobies and considerably larger than that of S. sula (SOM 3), but are smaller than those of S. magna . Based on a small sample, we could tentatively say that the pelvis shows a conspicuous lateral crest on the spina dorsolateralis ilii, which is also found in S. leucogaster but shallow, and completely absent in S. variegata .
A C B E 10 mm D
Remarks.—Although S. figueroae has a notably robust skull roof, it is narrow at the occipital region. This, however, does not affect the overall conical shape of the skull. Among the postcranial elements, the humerus is remarkable because of its proportions, being quite short relative to the proximal and distal widths. Thus, the humerus length is the same of S. nebouxii , even though its distal and proximal widths equal those of S. tasmani and S. dactylatra , which in turn are quite longer. The proportions concerning the length of the other postcranial bones of S. figueroae in comparison with other Sula species should be carefully addressed because of the limited sampling of the fossil (only two incomplete specimens). Warheit (1992) and Stucchi (2010) have already noted the importance of the quantity of specimens when evaluating the trends in dimensions and proportions (i.e. intraspecific variation) in a species. Despite that, the morphology and morphometric data of this extinct booby are more in line with the feeding and hunting strategies of its extant relatives, having the same basic body plan of the genus.
Genus Ramphastosula Stucchi and Urbina, 2004
Type species: Ramphastosula ramirezi Stucchi and Urbina, 2004 , Sacaco Sur locality (Poza Roja), Pisco Formation ( Peru), Messinian (Late Miocene).
Emended diagnosis.— Ramphastosula can be diagnosed from other sulids by the following combination of characters: (i) height of the rostrum at its mid-length is more than half the height at the nasofrontal hinge; (ii) slightly to strongly convex rostrum in all its dorsal edge; (iii) leromedially compressed rostrum forming a triangle in anterior view, in which the dorsal surface shows a strong ridge; (iv) well-developed occipital and temporal regions; (v) broad paroccipital procceses of the exoccipitals projecting laterally to the level of the postorbital processes; (vi) broad temporal fossae; (vii) robust frontal region.
Ramphastosula ramirezi Stucchi and Urbina, 2004 Emended diagnosis.—Height of the rostrum at its mid-length is higher than the height at the nasofrontal hinge, and all its dorsal edge is strongly convex.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
