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A new Cretaceous Metatherian mammal from Henan, China.

Bi S, Jin X, Li S, Du T - PeerJ (2015)

Bottom Line: The new taxon, Lotheridium mengi, is based on a nearly complete skull and associated lower jaws with full adult dentition.Previous views on deltatheroidan relationships were diverse, but recent studies favored their metatherian affinity.The new species also indicates that deltatheroidan mammals were more diverse and had broader geographical distributions than previously thought.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences , Beijing , China ; Department of Biology, Indiana University of Pennsylvania , Indiana, PA , United States of America.

ABSTRACT
We report a new deltatheroidan mammal from the Upper Cretaceous of Henna, China. The new taxon, Lotheridium mengi, is based on a nearly complete skull and associated lower jaws with full adult dentition. Deltatheroidans are known mostly from fragmentary specimens from Asia and North America. Previous views on deltatheroidan relationships were diverse, but recent studies favored their metatherian affinity. The new specimen represents the most complete skull known for deltatheroidans and provides additional evidence that deltatheroidans already had the distinctive metatherian dental formula and replacement pattern and several other derived metatherian features, supporting the metatherian status for this clade. The new species also indicates that deltatheroidan mammals were more diverse and had broader geographical distributions than previously thought.

No MeSH data available.


The skull of Lotheridium mengi (ZMNH M9032).(A) The lateral view of the right side of the skull. (B) The skull in occipital view. (C) The skull in rostral view. (D) Explanatory drawing of the basiocranium. (E) The close-up view of the basiocranium. bo, basioccipital; bs, basisphenoid; eo, exoccipital; fv, fenestra vestibuli; fm, foramen magnum; fs, facial sulcus; gf, glenoid fossa; hf, hypoglossal foramen; iof, infraorbital foramen; ju, jugal; lac, lacrimal; mb, mandible; mx, maxillae; oc, occipital condyle; pgf, postglenoid foramen; pgp, postglenoid process; pmx, premaxilla; pr, promontorium; so, supraoccipital; sq, squamosal.
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fig-2: The skull of Lotheridium mengi (ZMNH M9032).(A) The lateral view of the right side of the skull. (B) The skull in occipital view. (C) The skull in rostral view. (D) Explanatory drawing of the basiocranium. (E) The close-up view of the basiocranium. bo, basioccipital; bs, basisphenoid; eo, exoccipital; fv, fenestra vestibuli; fm, foramen magnum; fs, facial sulcus; gf, glenoid fossa; hf, hypoglossal foramen; iof, infraorbital foramen; ju, jugal; lac, lacrimal; mb, mandible; mx, maxillae; oc, occipital condyle; pgf, postglenoid foramen; pgp, postglenoid process; pmx, premaxilla; pr, promontorium; so, supraoccipital; sq, squamosal.

Mentions: The skull length (from the tip of the premaxilla to the posterior border of the occipital condyles) is 67.3 mm. The snout is short, less than a third of the length of the entire skull (Figs. 1A–1B and 2A). The tip of the snout has been broken and the left premaxilla is missing. The premaxilla forms the floor and lateral walls of the external nasal aperture and wedges dorsoposteriorly between the nasal and maxilla (Figs. 2A and 2C). In ventral view, the premaxilla is a short element that contains incisors I1-I4 (Figs. 1C and 4B). Its posterior border contributes to the anteromedial rim of the alveolus for the upper canine. There is a large depression for the tip of the lower canine between I4 and C. The incisive foramen is discernable medial to the alveoli of I2-4 and the depression (Fig. 1C). Most of the foramen is within the premaxilla and the maxilla forms the posterior border, as in Monodelphis. The paired nasal bones are parallel sided for most of their anterior length, and strongly expand posteriorly. The contact between the nasal and frontal is very broad although the nasofrontal suture cannot be ascertained due to the breakage. The maxilla contacts the nasal dorsally, the jugal and lacrimal dorsoposteriorly, but does not reach the frontal (Figs. 1A, 1B, 1D and 2A). It has a large facial process that is the major element of the lateral wall of the snout. The infraorbital foramen is large, dorsal to the posterior root of P3. The maxilla anterior to the foramen is concave, perhaps representing an attachment for the facial musculature. The maxilla contributes little to the zygomatic arch but forms the floor of the orbit. The lacrimal borders the orbit anteriorly and has a sizable expansion on the facial region (Figs. 1A–1B and 2A). It contacts the jugal posterolaterally, the maxilla anteriorly and the nasal and frontal dorsally. There are two lacrimal foramina along the anterior emargination of the orbit, separated by a distinct lacrimal tubercle. Within the orbit, the lacrimal contributes to the roof of the posterior opening of the infraorbital canal and anteromedial wall of the orbit. The anterior margin of the orbit is level with the anterior root of M1. The frontal is short and only forms the mid-section of the skull roof (Figs. 1A–1B). In dorsal view, the frontal bears a blunt postorbital process. Just posterior to the processes, the low temporal lines converge gradually posteriorly and meet at the frontal-parietal suture to form a sagittal crest. The postorbital constriction is situated at the frontal-parietal suture. In lateral view, the frontal contributes the anteromedial wall of the orbit, but its contact with other elements in the ventral region of the orbit is crushed. The parietal is large and forms the bulk of the skull roof (Figs. 1A–1B). Unlike the end-to-end interdigtated contact of the nasal and frontal, the parietal dorsally overlaps the frontal at their contact. A low sagittal crest runs from the anterior ends of the parietals to the lambdoidal crest. The parietal contacts the squamosal posteroventrally and forms the central portion of the lambdoidal crest. The jugal is robust and forms the main body of the zygoma. It extends anteriorly to contact the lacrimal and maxilla and posteriorly the jugal is dorsally overlapped by the squamosal zygoma (Figs. 1D and 2A). At the midpoint of the arched zygoma, there is a dorsal process of the jugal that marks the posteroventral border of the orbit (Fig. 1A). Its posterior end forms the anterolateral wall of the glenoid fossa (Figs. 2D–2E). The palatine is very extensive and extends far posteriorly behind the last molar and lacks palatal vacuities (Fig. 1C). The anterior extent of the palatine is unclear because of the breakage in the area. The squamosal forms the posterior sidewall of the braincase (Figs. 1A and 2A). The zygomatic process of the squamosal is short, overlying the jugal anteriorly. In ventral view, the glenoid fossa is transversely elongated, located entirely on the posterior zygomatic root (Figs. 2D–2E). Behind the fossa, there is a stout postglenoid process. The postglenoid foramen is medial to the process. The basicranium is badly fractured anteriorly; the choanal area in front of the basisphenoid can not be interpreted (Figs. 1C and 2E). The basisphenoid bone occupied the midline of the basicranium and widens posteriorly to its suture with the basiocciptal (Figs. 2D–2E). Its ventral surface is flat, flanked by rounded raised lateral ridges. The basioccipital forms the skull base and is fused with the basisphenoid anteriorly in a straight suture. Its posterior side is indented by a V-shaped intercondyloid notch. Lateral to the notch, the occipital condyles are large and protrude posteriorly. The hypoglossal foramen is located anterior to the condyle. In the middle ear region, the promontorium of the petrosal is well preserved on each side. It is bulbous-shaped and abuts to the posterolateral border of the basioccipital (Figs. 2D–2E). The anteroventral surface of the promontorium is excavated by a shallow, anteromedially directed sulcus for facial nerve. The fenestra vestibuli occupies the posterolateral corner of the promontorium and faces laterally. The surface of the promontorium is similar to that in Deltatheridium in lacking vascular grooves, but detailed description and comparisons await CT data. The other foramina and sulci are hard to determine because they are obliterated or masked by fractures. The supraoccipital bears a strong lambdoidal crest that projects slightly posteriorly (Fig. 2B). The exocciptials form most of the dorsolateral wall of the foramen magnum and also contribute to the dorsoposterior part of the occipital condyles.


A new Cretaceous Metatherian mammal from Henan, China.

Bi S, Jin X, Li S, Du T - PeerJ (2015)

The skull of Lotheridium mengi (ZMNH M9032).(A) The lateral view of the right side of the skull. (B) The skull in occipital view. (C) The skull in rostral view. (D) Explanatory drawing of the basiocranium. (E) The close-up view of the basiocranium. bo, basioccipital; bs, basisphenoid; eo, exoccipital; fv, fenestra vestibuli; fm, foramen magnum; fs, facial sulcus; gf, glenoid fossa; hf, hypoglossal foramen; iof, infraorbital foramen; ju, jugal; lac, lacrimal; mb, mandible; mx, maxillae; oc, occipital condyle; pgf, postglenoid foramen; pgp, postglenoid process; pmx, premaxilla; pr, promontorium; so, supraoccipital; sq, squamosal.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400878&req=5

fig-2: The skull of Lotheridium mengi (ZMNH M9032).(A) The lateral view of the right side of the skull. (B) The skull in occipital view. (C) The skull in rostral view. (D) Explanatory drawing of the basiocranium. (E) The close-up view of the basiocranium. bo, basioccipital; bs, basisphenoid; eo, exoccipital; fv, fenestra vestibuli; fm, foramen magnum; fs, facial sulcus; gf, glenoid fossa; hf, hypoglossal foramen; iof, infraorbital foramen; ju, jugal; lac, lacrimal; mb, mandible; mx, maxillae; oc, occipital condyle; pgf, postglenoid foramen; pgp, postglenoid process; pmx, premaxilla; pr, promontorium; so, supraoccipital; sq, squamosal.
Mentions: The skull length (from the tip of the premaxilla to the posterior border of the occipital condyles) is 67.3 mm. The snout is short, less than a third of the length of the entire skull (Figs. 1A–1B and 2A). The tip of the snout has been broken and the left premaxilla is missing. The premaxilla forms the floor and lateral walls of the external nasal aperture and wedges dorsoposteriorly between the nasal and maxilla (Figs. 2A and 2C). In ventral view, the premaxilla is a short element that contains incisors I1-I4 (Figs. 1C and 4B). Its posterior border contributes to the anteromedial rim of the alveolus for the upper canine. There is a large depression for the tip of the lower canine between I4 and C. The incisive foramen is discernable medial to the alveoli of I2-4 and the depression (Fig. 1C). Most of the foramen is within the premaxilla and the maxilla forms the posterior border, as in Monodelphis. The paired nasal bones are parallel sided for most of their anterior length, and strongly expand posteriorly. The contact between the nasal and frontal is very broad although the nasofrontal suture cannot be ascertained due to the breakage. The maxilla contacts the nasal dorsally, the jugal and lacrimal dorsoposteriorly, but does not reach the frontal (Figs. 1A, 1B, 1D and 2A). It has a large facial process that is the major element of the lateral wall of the snout. The infraorbital foramen is large, dorsal to the posterior root of P3. The maxilla anterior to the foramen is concave, perhaps representing an attachment for the facial musculature. The maxilla contributes little to the zygomatic arch but forms the floor of the orbit. The lacrimal borders the orbit anteriorly and has a sizable expansion on the facial region (Figs. 1A–1B and 2A). It contacts the jugal posterolaterally, the maxilla anteriorly and the nasal and frontal dorsally. There are two lacrimal foramina along the anterior emargination of the orbit, separated by a distinct lacrimal tubercle. Within the orbit, the lacrimal contributes to the roof of the posterior opening of the infraorbital canal and anteromedial wall of the orbit. The anterior margin of the orbit is level with the anterior root of M1. The frontal is short and only forms the mid-section of the skull roof (Figs. 1A–1B). In dorsal view, the frontal bears a blunt postorbital process. Just posterior to the processes, the low temporal lines converge gradually posteriorly and meet at the frontal-parietal suture to form a sagittal crest. The postorbital constriction is situated at the frontal-parietal suture. In lateral view, the frontal contributes the anteromedial wall of the orbit, but its contact with other elements in the ventral region of the orbit is crushed. The parietal is large and forms the bulk of the skull roof (Figs. 1A–1B). Unlike the end-to-end interdigtated contact of the nasal and frontal, the parietal dorsally overlaps the frontal at their contact. A low sagittal crest runs from the anterior ends of the parietals to the lambdoidal crest. The parietal contacts the squamosal posteroventrally and forms the central portion of the lambdoidal crest. The jugal is robust and forms the main body of the zygoma. It extends anteriorly to contact the lacrimal and maxilla and posteriorly the jugal is dorsally overlapped by the squamosal zygoma (Figs. 1D and 2A). At the midpoint of the arched zygoma, there is a dorsal process of the jugal that marks the posteroventral border of the orbit (Fig. 1A). Its posterior end forms the anterolateral wall of the glenoid fossa (Figs. 2D–2E). The palatine is very extensive and extends far posteriorly behind the last molar and lacks palatal vacuities (Fig. 1C). The anterior extent of the palatine is unclear because of the breakage in the area. The squamosal forms the posterior sidewall of the braincase (Figs. 1A and 2A). The zygomatic process of the squamosal is short, overlying the jugal anteriorly. In ventral view, the glenoid fossa is transversely elongated, located entirely on the posterior zygomatic root (Figs. 2D–2E). Behind the fossa, there is a stout postglenoid process. The postglenoid foramen is medial to the process. The basicranium is badly fractured anteriorly; the choanal area in front of the basisphenoid can not be interpreted (Figs. 1C and 2E). The basisphenoid bone occupied the midline of the basicranium and widens posteriorly to its suture with the basiocciptal (Figs. 2D–2E). Its ventral surface is flat, flanked by rounded raised lateral ridges. The basioccipital forms the skull base and is fused with the basisphenoid anteriorly in a straight suture. Its posterior side is indented by a V-shaped intercondyloid notch. Lateral to the notch, the occipital condyles are large and protrude posteriorly. The hypoglossal foramen is located anterior to the condyle. In the middle ear region, the promontorium of the petrosal is well preserved on each side. It is bulbous-shaped and abuts to the posterolateral border of the basioccipital (Figs. 2D–2E). The anteroventral surface of the promontorium is excavated by a shallow, anteromedially directed sulcus for facial nerve. The fenestra vestibuli occupies the posterolateral corner of the promontorium and faces laterally. The surface of the promontorium is similar to that in Deltatheridium in lacking vascular grooves, but detailed description and comparisons await CT data. The other foramina and sulci are hard to determine because they are obliterated or masked by fractures. The supraoccipital bears a strong lambdoidal crest that projects slightly posteriorly (Fig. 2B). The exocciptials form most of the dorsolateral wall of the foramen magnum and also contribute to the dorsoposterior part of the occipital condyles.

Bottom Line: The new taxon, Lotheridium mengi, is based on a nearly complete skull and associated lower jaws with full adult dentition.Previous views on deltatheroidan relationships were diverse, but recent studies favored their metatherian affinity.The new species also indicates that deltatheroidan mammals were more diverse and had broader geographical distributions than previously thought.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences , Beijing , China ; Department of Biology, Indiana University of Pennsylvania , Indiana, PA , United States of America.

ABSTRACT
We report a new deltatheroidan mammal from the Upper Cretaceous of Henna, China. The new taxon, Lotheridium mengi, is based on a nearly complete skull and associated lower jaws with full adult dentition. Deltatheroidans are known mostly from fragmentary specimens from Asia and North America. Previous views on deltatheroidan relationships were diverse, but recent studies favored their metatherian affinity. The new specimen represents the most complete skull known for deltatheroidans and provides additional evidence that deltatheroidans already had the distinctive metatherian dental formula and replacement pattern and several other derived metatherian features, supporting the metatherian status for this clade. The new species also indicates that deltatheroidan mammals were more diverse and had broader geographical distributions than previously thought.

No MeSH data available.