The largest sauropodomorph skull from the Lower Jurassic Lufeng Formation of China

Skull

The skull of LFGT-ZLJ0011 is relatively large with thin vertically supportive bones. It seems to have undergone severe transverse compression, resulting in the distortion of its dorsal and palatal elements (Figs. 2–4). However, the two lateral sides of the skull are essentially intact, except for some missing bones in the orbital and temporal regions, such as the postorbital, jugal, quadratojugal and squamosal, which were displaced from their life position or even lost (Figs. 2 and 3). The skull is low and elongated in lateral view with an anteroposterior length of 40 cm (based on the left mandibular length), making it the largest cranial material recovered from the Lufeng Formation, while the previously largest is the skull of Jingshanosaurus, which is about 35 cm long (Zhang et al., 2020).

Most of the skull openings of LFGT-ZLJ0011 are broken; therefore, the shapes of the orbit, supratemporal, and infratemporal fenestra are difficult to deduce with certainty. The right external naris is large with the anteroposterior length accounting for approximately 22% of the total skull length, which is similar to the 20% ratio of Jingshanosaurus (Zhang et al., 2020), but that of Yunnanosaurus is only 10% (Barrett et al., 2007). This opening is subtriangular in shape and bordered by the premaxilla (anteroventrally), maxilla (posteriorly), and nasal (dorsally) (Fig. 2). The posterior margin of this opening is located posterior to the premaxilla-maxilla suture; however, it is anterior to the anterior margin of the antorbital fenestra, which is different from that of Jingshanosaurus (Zhang et al., 2020). The posteroventral corner of the external naris is at an obtuse angle, resembling that of Yizhousaurus (LFGT-ZLJ0033); however, this angle is acute in Yunnanosaurus (IVPP V 20/NJGM 004546) and forms a right angle in Jingshanosaurus (LFGT-ZLJ0113 and CXM-LT9401). In right lateral view, the antorbital fenestra appears to form an approximate equilateral triangle (Fig. 2), which is similar to that of Lufengosaurus (IVPP V 15); however, it is broader anteroposteriorly than those of Yizhousaurus (Zhang et al., 2018). This opening of LFGT-ZLJ0011 is set within a triangular antorbital fossa, which is deeply impressed on the maxilla anteroventrally (Figs. 2 and 3).

Premaxilla. The premaxilla has a subtriangular shape in lateral view, forming the anterior end of the snout as well as the anteroventral margin of the external naris (Figs. 2 and 3). The premaxilla contacts the maxilla posteriorly and the nasal dorsally. It projects two processes, the anterodorsal nasal process and the posterolateral maxillary process, arising from the main body. The lateral surface of the premaxillary body is slightly convex, while its ventral margin is level with that of the maxilla. On the anterolateral surface of the premaxillary body, three neurovascular foramina are present in a subvertical row, which are more visible on the left premaxilla (Fig. 3) and at least two can be identified on the right side (Fig. 2). This foramina arrangement is similar to those of Adeopapposaurus (Martínez, 2009), Jingshanosaurus (CXM-LT9401) and Massospondylus (Sues et al., 2004).

The nasal process of the premaxilla extends posterodorsally and forms most of the anterior margin of the external naris. In lateral view, this process is anteroposteriorly expanded at its base where it joins the premaxillary body and posterodorsally tapers and elongates to its distal end (Fig. 2). The inflection at the base of the premaxillary nasal process is absent in LFGT-ZLJ0011, different from those of Jingshanosaurus (CXM-LT9401) and Melanorosaurus (NM QR3314).

The maxillary process extends posteriorly from the dorsal margin of the premaxilla, forming the ventral margin of the external naris. This process is a flat strap structure that overlaps the anterodorsal region of the premaxillary process of the maxilla (Figs. 2 and 3). In lateral view, the dorsoventral height of the maxillary process accounts for approximately 30% of the total premaxillary body height. The ventral margin of the maxillary process and the posterior margin of the premaxillary body form an ‘L’-shaped suture between the premaxilla and maxilla, and define a conspicuous subnarial foramen exposed externally below the maxillary process (Fig. 3).

Maxilla. The posterior-most regions of both maxillae are fractured, lacking posterior contacts with the jugal and lacrimal. The remaining maxilla contacts the premaxilla anteriorly, and the lacrimal and nasal dorsally, forming the posteroventral margin of the naris, as well as the anterior and ventral margins of the antorbital fenestra. The maxilla has a triradiate lateral profile comprising three processes: the anterior premaxillary, the posterior jugal, and the posterodorsal ascending processes (Figs. 2 and 3). In lateral view, the maxilla is long and straight anteroposteriorly, with its dorsal and ventral margins parallel to each other. The maxilla is at its dorsoventral highest anteriorly and tapers towards its posterior end. A linear row with at least six neurovascular foramina is present on the lateral surface of the right maxilla, most of which are ventro- or postero-laterally oriented (Fig. 2). They are evenly spaced and similarly sized, and the posterior-most one is not larger than the anterior ones (Fig. 2), which is characterized and different from other non-sauropodan sauropodomorphs (Plateosauridae and Massospondylidae) with a distinctly larger foramen at the posterior end. There is no evidence of a lateral maxillary ridge, which differs from those of Lufengosaurus (Barrett & Upchurch, 2005) and Melanorosaurus (Yates, 2007). The alveolar region of the maxilla is not developed, indicating that the ‘lateral plate’ is absent; however, it is preserved in Aardonyx (Yates et al., 2010) and Yizhousaurus (Zhang et al., 2018).

The premaxillary process is sub-rectangular and the shortest of the three processes. The anterodorsal region of this process is overlapped by the maxillary process of the premaxilla (Fig. 3). Its anteroposterior length is a little greater than its dorsoventral depth, which is different from Jingshanosaurus (both LFGT-ZLJ0113 and CXM LT-9401) that has a shorter premaxillary process of the maxilla. The dorsal surface of the premaxillary process is slightly inclined and orientated dorsolaterally, forming the maxillary region of the narial fossa.

The ascending process of the maxilla is slender and much less anteroposteriorly expanded than in most Lufeng sauropodomorphs, such as Lufengosaurus (IVPP V 15), Yunnanosaurus (IVPP V 20/NJGM 004546), Xingxiulong (LFGT-D0003) and Yizhousaurus (LFGT-ZLJ0033). Although the maxillary ascending processes of Jingshanosaurus (LFGT-ZLJ0113) are not well preserved, those of CXM LT-9401 are also anteroposteriorly expanded, especially at the top. This process arises from a point approximately one-third of the anteroposterior length of the maxilla and gradually inclines posterodorsally (Figs. 2 and 3). It forms the posterior margin of the external naris, thereby separating the maxillary processes of the premaxilla and nasal. The ascending process possesses a distinct ridge that runs along the midline of its entire lateral surface (Fig. 2). The anterodorsal region of the ascending process is overlapped by the ventrolateral process of the nasal, and the posterodorsal region contacts the lacrimal. The posteroventral surface of the ascending process is excavated, forming a thin subtriangular medial lamina of the antorbital fossa, as in Adeopapposaurus (Martínez, 2009), Jingshanosaurus (CXM-LT9401), Massospondylus (Sues et al., 2004), and Mussaurus (Pol & Powell, 2007), different from the anteroposteriorly broad medial lamina of Coloradisaurus (Apaldetti et al., 2014), Lufengosaurus (IVPP V 15), Melanorosaurus (Yates, 2007), Plateosaurus (Prieto-Márquez & Norell, 2011), Riojasaurus (Bonaparte & Pumares, 1995) and Unaysaurus (Leal et al., 2004).

Nasal. Although both nasals are preserved, the right one is better preserved than the left; however, the midline suture between the two is difficult to determine owing to the compression. The nasal comprises an anterior premaxillary process, a ventral maxillary process, and a posterior process (Fig. 2). In lateral view, the dorsal and lateral surfaces of the nasal are slightly convex without a depression posterior to the naris, which is present in Adeopapposaurus (Martínez, 2009), Lufengosaurus (IVPP V 15), Massospondylus (Sues et al., 2004) and Plateosaurus (Prieto-Márquez & Norell, 2011).

The anteriorly extending premaxillary process forms the anterodorsal margin of the external naris. The mediolateral width of the premaxilla process of the nasal at its base is less than the anteroposterior width of the maxilla process at its base (Fig. 3), which is considered to be an autapomorphy of Lishulong, given that this condition is opposite in almost all non-sauropodan sauropodomorphs. The premaxillary process gradually curves and tapers anteroventrally to a lap joint that contacts the premaxillary nasal process medially (Figs. 2 and 3). The posterior process is anteroposteriorly shorter than the premaxillary process, and its posterior region is broken. It extends posteriorly to contact the anterior end of the frontal and the medial surface of the prefrontal; however, these three elements are disarticulated (Fig. 3).

In lateral view, the maxillary process of the nasal is a subtriangular sheet of bone that tapers sharply as it extends ventrally (Fig. 2). It contacts the anterolateral surface of the ascending process of the maxilla and extends for approximately half of the dorsoventral height of the ascending process, as present in many early sauropodomorphs (e.g., Coloradisaurus, Lufengosaurus, Massospondylus and Yunnanosaurus). The posterodorsal region of the maxillary process partially contributes to the anterodorsal margin of the antorbital fossa and overlaps the lacrimal with short contact.

Lacrimal. The right lacrimal is well-preserved and undistorted; however, only a third of the dorsal region of the left one is preserved, which falls on the anteroventral corner of the antorbital fenestra (Fig. 3). The lacrimal initially contacts the maxilla and nasal anterodorsally, the prefrontal posterodorsally, and the maxilla and jugal ventrally. It contains an anteroventrally directed short process and a posteroventrally oriented main shaft. In lateral view, the two rami meet at approximately 90° to each other, forming an inverted ‘L’-shape (Fig. 2). The anterior process is anteroposteriorly short with a rounded vertex, forming a small, triangular shelf that overhangs the posterodorsal corner of the antorbital fenestra. The main shaft of the lacrimal is an anteroposteriorly thin and dorsoventrally tall structure with a deep groove posteriorly opening lateral to it, indicating the posterior opening of the foramen for the nasolacrimal duct (Figs. 2 and 3). Although the morphology of the lacrimal is similar to that of other Lufeng taxa, that of Lishulong is significantly more elongated and thinner with a smaller dorsal process. The ventral region of the lacrimal shaft is posteroventrally expanded, forming a subtriangular, rugose surface for contacting the anterior process of the jugal.

Prefrontal. Only part of the left prefrontal is preserved and displaced posteriorly from its natural position. Logically, the prefrontal contacts the nasal anteriorly, the lacrimal anteroventrally, and the frontal posteromedially. The remaining region of the prefrontal is dorsoventrally flattened with a tab-like structure exposed on the skull roof (Fig. 3). The posterior region of the prefrontal has an overlapped contact with the frontal, which borders it posteriorly and medially.

Frontal. The right frontal is also missing, and the left one is incompletely preserved. The frontal is a sub-trapezoidal, thick plate that is anteroposteriorly longer than it is transversely wide (Fig. 3), although its posterior end is broken, different from the wider frontal of Yizhousaurus (LFGT-ZLJ0033). The anterior region of the frontal is narrow and tab-like with a rounded distal margin, overlapped by the prefrontal, and its suture with the nasal cannot be determined accurately due to poor preservation. The dorsal surface of the frontal is gently concave, bearing a shallow depression. The lateral margin of the frontal is thickened, while the posterior margin of the frontal is linear and contacts the anterior margin of the parietal.

Postorbital. The right postorbital is preserved with the ventral process fractured. It is a triradiate bone that comprises the ventral jugal process, as well as the anteriorly and posteriorly directed dorsal processes (Fig. 2). Every process separates from an angle of approximately 120° to the other two. The anterodorsal process of the postorbital is dorsoventrally compressed and mediolaterally widened into a tab-like structure. The dorsal surface of the anterodorsal process is convex. The posterodorsal process of the postorbital is typically shorter than the other two processes, it has a subtriangular tip and tapers posteriorly, where it contacts the squamosal.

Jugal. The posterior-half region of the left jugal is preserved; however, it is disarticulated from the buccal area. It has two posterior processes left: the posterodorsal postorbital process and the posterior quadratojugal process, together forming a sideways ‘V’-shaped opening directed posteriorly (Fig. 3), which sets an angle of approximately 60 degrees, resembling that of Yunnanosaurus (Barrett et al., 2007), but smaller than those in Plateosaurus (80 degrees or 95 degrees; Prieto-Márquez & Norell, 2011) and Xingxiulong (80 degrees), larger angle than those in Lufengosaurus (50 degrees; Barrett, Upchurch & Wang, 2005), Massospondylus (40 degrees; Chapelle & Choiniere, 2018), Mussaurus (50 degrees; Pol & Powell, 2007). The quadratojugal process is slender and elongated, and tapers out posteriorly as it contacts the quadratojugal. The postorbital process projects posterodorsally from the main body of the jugal. It is relatively short and slightly curved, dorsally tapering to contact the ventral process of the postorbital.

Quadrate. Both quadrates are preserved, and the left one is more complete than the right one, even though the former is dislocated over a distance (Fig. S1A). The quadrate forms the posterolateral margin of the skull that would articulate with the mandible. The quadrate comprises a quadrate head, a main shaft, a lateral quadratojugal process, and a medial pterygoid process. In lateral view, the quadrate head is subtriangular and mediolaterally compressed (Fig. 3). The main shaft is robust and slightly bowed anteriorly with its posterior surface shallowly excavated along its length. The posterior margin of the quadrate shaft is thickened into a ridge-like structure that extends from the quadrate head to the quadrate condyles. The quadrate foramen is present below the dorsal half of the posterior surface, lateral to the ridge of the main shaft (Figs. 3 and 4A). Distally, the shaft expands both anteroposteriorly and transversely to form the articulation that contacts the mandible. This articular region is divided into two semicircular lateral and medial condyles by a deep intercondylar groove. The posteromedial margin of the medial condyle is more ventrally located than that of the lateral one.

The pterygoid process of the quadrate extends anteriorly as a mediolateral sheet element that occupies more than two-thirds of the dorsal quadrate shaft. The dorsal region of the pterygoid process grades gradually into the quadrate head (Fig. 3). It forms an extensive articulation with the quadrate process of the pterygoid along its entire anterior margin. The quadratojugal process extends anterolaterally from the dorsal half of the quadrate shaft, at an angle of approximately 90° with the pterygoid process. The two processes of the quadrate are set at an angle of less than 90° and separated by a large concave area on the anterior surface of the quadrate (Fig. 2).

Pterygoid. The incomplete left pterygoid is exposed in the right lateral and ventral views (Figs. 2 and 4B). The pterygoid makes up most of the posterior region of the palate and contacts the quadrate posterolaterally. The pterygoid comprises three sections: the central region, the anterior palatine process, and the quadrate process. The palatine process of the pterygoid is fractured together with the anterior palatal bones, including the vomer and palatine. The central region of the pterygoid is complex, it projects a short medial process to contain the basipterygoid process, and a lateral flange anterior to the quadrate process (Fig. S1B). The lateral flange is robust and contacts the ectopterygoid dorsally. The quadrate process is a large lamina that curves posterolaterally from the central region of the pterygoid. It is concave along its medial surface and convex laterally, and overlapped by the pterygoid process of the quadrate medially.

Supraoccipital. The supraoccipital is well-preserved and sloped anterodorsally. In posterior view, it has a roughly pentagonal outline and it is transversely wider than dorsoventrally high (Fig. S1), which differs from the typical higher supraoccipitals present in most non-sauropodan sauropodomorphs, except Ngwevu (Chapelle et al., 2019). The supraoccipital contacts the exoccipital ventrolaterally, its lateral margin contributes to the base of the paroccipital processes of the exoccipitals. The posterodorsal surface of the supraoccipital contains a low and rounded median ridge that extends dorsoventrally along the midline of the supraoccipital. On the dorsal end of the median ridge is a notch, which is presumed to be the post-parietal fenestra (Fig. S1A). The ventral margin of the supraoccipital forms two prominent protuberances, forming the dorsolateral margin of the foramen magnum.

Exoccipital-opisthotic. The exoccipital is relatively complete and fused to the opisthotic as a complex element. It forms the lateral margin of the foramen magnum and the dorsolateral region of the occipital condyle (Fig. S1A). Each exoccipital contacts the ventral region of the supraoccipital and the dorsal region of the basioccipital. The paroccipital process with a blunt, rounded distal end projects posteriorly and ventrolaterally (Fig. 3). This process has a straight or slightly convex dorsal margin and a concave ventral margin.

Basioccipital. The basioccipital is completely preserved and undistorted. It contacts the exoccipital dorsally and the basisphenoid anteriorly to form the ventral margin of the foramen magnum and the posterior region of the braincase (Fig. S1). The basioccipital expands posteriorly to form the occipital condyle, which appears as a sub-crescent in posterior view. In ventral view, it appears separated from the basal tubera by a constricted neck. On the ventral side of the condylar neck, there is a shallow vertical fissure. The basioccipital contacts part of the basisphenoid along its anterior surface; however, the suture is sinuous, and only an anteroposteriorly compressed ridge signifies the remnant of the basal tuberae.

Mandible

Both mandibles of LFGT-ZLJ0011 are present and complete in general, only the posterior region of the right mandibular ramus is broken and not as well preserved as the left one. The mandible is slender and elongated, with a long retroarticular process (Fig. 3). The external mandibular fenestra has a sub-elliptical outline in lateral view, and its anteroposterior length is approximately 11% of the total mandibular length, similar to the condition of Jingshanosaurus (LFGT-ZLJ0113), contrary to the relatively large size in most non-sauropodan sauropodomorphs. It is bounded anteriorly by the dentary, posterodorsally by the surangular, and posteroventrally by the angular. The coronoid eminence is developed, similar to those of Lufengosaurus (IVPP V 15) and Yunnanosaurus (IVPP V 20/NJGM 004546), which is approximately twice the height of the tooth-bearing part of the dentary. The jaw articulation is on the same level as the dentary tooth row, resembling the condition in Yunnanosaurus (IVPP V 20/NJGM 004546) and Xingxiulong (LFGT-D0003).

Dentary. The dentary makes up approximately more than half the total mandibular length. It maintains an almost constant height along its length with a slight increase in depth towards its posterior region (Figs. 2 and 3). The ratio of the height to length of the dentary is about 0.23, which is higher than that of other early sauropodomorphs (<0.2); however, it is lower than the ratio of 0.28 of Jingshanosaurus (LFGT-ZLJ0113). In lateral view, the anterior end of the dentary is subtriangular with a rounded tip. The lateral surface of the dentary is gently convex and the dorsal margin is pierced by a linear row of subequal neurovascular foramina (Figs. 2 and 3). Posteriorly, the dentary delimits the anterior margin of the external mandibular fenestra, eventually splitting into two processes that contact the surangular posterodorsally and the angular posteroventrally.

Surangular. In lateral view, the surangular is an elongated, sigmoidal element (Fig. 3). The lateral surface of the surangular is slightly convex, with its ventral margin forming most of the posterodorsal margin of the external mandibular fenestra. The surangular reaches its dorsoventrally largest depth at the level of the coronoid eminence, its dorsal margin thickened and oriented transversely to form the dorsal region of the coronoid. The medial surface is concave, forming a groove on the medial side of the mandible. The surangular contacts the dentary and splenial anteriorly, the angular ventrally, and the articular posteromedially to form the retroarticular process. The retroarticular process is finger-like with a concave dorsal surface at the jaw joint region.

Angular. The angular is a strap-like element that makes up the posteroventral region of the mandible. It has a broad contact with the surangular dorsally while articulating with the dentary anteriorly, and its dorsal margin forms the ventral border of the external mandibular fenestra (Figs. 2 and 3). In ventral view, the angular meets the prearticular along an almost straight anteroposterior suture with its medial surface being overlapped by the latter (Fig. S1).

Intercoronoid. There is some indication of an anteroposteriorly elongated intercoronoid that is located on the dorsomedial margin of the left mandible (Fig. 2). The intercoronoid is a thin bony plate that covers the lingual alveolar of the dentary. It is approximately 6 mm with a constant dorsoventral depth.

Splenial. The splenial is a flat, laminar bone that covers the dentary medially with its dorsal margin partially overlapping the intercoronoid (Fig. 2). The anterior region of the splenial is damaged, and no splenial foramen is visible, whereas the rest of it splits into two processes posteriorly. The sutures with the dentary, angular and prearticular could not be determined.

Prearticular. The prearticular is preserved and exposed in medial view (Fig. 2). It is an elongated, strap-like element that forms the medial region of the mandible’s posteroventral area. The dorsal surface of the prearticular is a shallowly concave midsection. Its posterior region comprises a portion of the retroarticular process medial surface and covers the medial surface of the articular.

Articular. The articular is a small block-like bone positioned dorsally to the prearticular and contacts the surangular laterally (Fig. 2). The dorsal surface of its anterior region is concave both anteroposteriorly and transversely for articulation with the quadrate. The articular has a blunt posterior tip that forms the medial region of the retroarticular process. There is a small, tab-like process directed medially posterior to the mandibular cotyle, this is also preserved in Xingxiulong (LFGT-D0003) and Jingshanosaurus (LFGT-ZLJ0113).

Ceratobranchial. A part of the left ceratohyal is preserved under the quadrate, medial to the left mandibular ramus (Figs. 2 and 4). It is elongated and rod-like with its anterior end expanded into a protuberance, and its posterior end is almost constant in diameter and slightly curves medially.

Dentition

In general, most of the teeth of LFGT-ZLJ0011 are well preserved, except for some left dentary teeth that are apically broken (Fig. 3). The morphology of the premaxillary teeth is nearly identical to that of the maxillary teeth. All the upper jaw teeth are more slender with apicobasal elongated crowns and appear to be more circular in the cross-section, leading to the inapparent mesiodistal constriction of the roots at the base. These teeth are linearly placed without overlapping crowns between adjacent teeth, with gaps visible between them in lateral view (Fig. 2; Fig. S2), instead of the typical imbricated arrangement. The crowns are apicobasally longer than they are mesiodistally wide. The tooth crowns display no distal recurvature, differing from the distally recurved crowns of Jingshanosaurus (LFGT-ZLJ0113). Coarse serrations are restricted to the apical half of the crown on both the mesial and distal carinae. The number of premaxillary teeth is clearly determined to be four, they are apicobasally higher than all the rear teeth. To determine the exact number of maxillary teeth is challenging because the posterior tooth rows are poorly preserved; however, at least 12 teeth are preserved on either side of the maxilla (Figs. 2 and 3). The labial surface of the tooth crown is slightly convex, whereas the lingual surface is slightly concave, which is different from the relatively flat lingual surfaces in other non-sauropodan sauropodomorphs and the highly concave condition in sauropods. The enamels of the teeth are smooth with gracile longitudinal striations, and finely wrinkled enamel has also been described in Jingshanosaurus (LFGT-ZLJ0113) and Irisosaurus (de Fabrègues et al., 2020). There is no indication of any genuine wear facets. The lower tooth row contains at least 20 teeth on the left side (Fig. 3), and the dentary teeth are smaller in size than the upper teeth.

Cervical vertebrae

Nine cervical vertebrae are preserved in the holotype (LFGT-ZLJ0011), including the axis along with eight associated cervicals (C3–C10); therefore, with the missing atlas, Lishulong should possess at least ten cervical vertebrae originally, which is typical condition for non-eusauropod sauropodomorphs. The neck is proportionally enlarged and elongated along with the skull. All the vertebrae are highly complete, and the centra are typically amphicoelous and solid inside without the evidence of camerae.

The well-preserved axis is much shorter than the postaxial cervical vertebrae. The centrum of the axis is slightly compressed laterally, and 3.4 times longer than it is high, which is slightly greater than that of Lufengosaurus (Young, 1941a), Jingshanosaurus (Zhang & Yang, 1995), and Xingxiulong (Wang, You & Wang, 2017). Its dorsal surface is almost flat along the neural canal, and its ventral surface bears a markedly longitudinal keel that runs along the anterior two-thirds of its ventral length. An incompletely preserved intercentrum is fused to the ventral region of the anterior surface of the axial centrum (Fig. 4); however, it is not broader than the width of the centrum in anterior view, which is different from that of Yizhousaurus (Zhang et al., 2018). The intercentrum is somewhat broken, its anteroposterior length is approximately one-eighth of the total central length. The neural canal is large, occupying more than half the anterior surface of the centrum. The posterior surface of the centrum is circular and concave. The neural arch is tightly fused to the centrum extending along almost its entire length (Fig. 4). The neural spine is damaged in its anterior region, and the remaining posterior half is subtriangular in dorsal view. The diapophyses are absent, whereas the parapophyses are situated ventrolaterally in the anterior region of the centrum, presenting as anteroposteriorly elongated tubercles (Fig. 4). The prezygapophyses are also inconspicuous on the anterolateral area of the neural arch. The postzygapophyses extend flush with the posterior surface of the centrum (Fig. 4). The epipophyses are developed as moderate ridges on the dorsal surface of the postzygapophyses, extending along their entire length.

The eight postaxial cervical vertebrae of LFGT-ZLJ0011 are completely preserved. All the cervical centra are more elongated and robust than those of other Lufeng sauropodomorphs, even more than twice the length of each cervical of Lufengosaurus (Young, 1941a), Yunnanosaurus (Young, 1942) and Xingxiulong (Wang, You & Wang, 2017). The third cervical has a remarkably elongated centrum, which is approximately 1.4 times the length of the axial element with a centrum length/height ratio is approximately 4.6. The abrupt elongation of cervical 3 is also observed in Coloradisaurus (Apaldetti, Pol & Yates, 2013), Lufengosaurus (Young, 1941a), and Yizhousaurus (Zhang et al., 2018); however, it differs from Yunnanosaurus (Young, 1942), in which the third cervical is only one-third longer than the axis. The centra of cervicals 4 to 7 gradually increase their length to the maximum, whereas cervicals 8 to 10 are progressively shorter. All these centra are compressed both laterally and ventrally with remarkably developed ventral keels, which become more noticeable in the posterior cervical vertebrae (Figs. 4 and 6). The neural arches are strongly fused to the centra with their heights lower than those of their respective centra (Fig. 4). The articular surfaces of the centra are sub-circular with shallowly concave anterior surfaces and deeply concave posterior surfaces, which is typically present in other early sauropodomorphs. The posterior surfaces of the centra in the anterior cervical vertebrae are subequal in height and width; however, the centra of cervicals 6 to 10 are not higher than they are wide, indicating dorsoventral compression of the posterior centra. The neural spines are low and elongated, becoming higher and thicker from the anterior to posterior cervical vertebrae. The anteroposterior length of the neural spines progressively increases up until cervical 7, and then becomes shorter posteriorly. The anterior ends of the dorsal surface of the neural spines are laterally expanded as two protuberances, and the posterior region appears as transversely thin plates in dorsal view, forming an anteroposterior sub-rhombic at the anterior half of the spines (Fig. 5), instead of laterally expanded tables at the midlength of the dorsal surface of the neural spines. This anterolateral expansion of the cervical neural spines is unique in LFGT-ZLJ0011; therefore, it is treated as one of the autapomorphies of Lishulong. The diapophyses are weakly developed in the anterior and middle cervicals, presenting as elongated ridges close to the anterior margins of the centra, in posterior vertebrae they form aliform flanks that become progressively larger (Fig. 4). The parapophyses are present as sub-elliptical protuberances situated at the anteroventral region of the lateral surfaces of the centra, except in the last two vertebrae in which they shift progressively to a more posterior position. The zygapophyses of most cervical vertebrae extend horizontally with flat articular facets; however, they are slightly upturned approximately 20° with respect to the centra in cervicals 9 and 10 (Fig. 4). The prezygapophyses develop distinct ventrolateral ridges, so the centroprezygapophyseal laminae are robust in anterior view, while the prezygodiapophyseal laminae are present only in both cervicals 9 and 10, not as developed as in derived sauropodiforms. Along with the cervical series, the prezygapophyses extend far beyond the anterior surface of the centra; however, the postzygapophyses are short and do not overhang to the posterior margin of the centra. The epipophyses are low ridges that extend along the dorsal surface of the postzygapophyses (Fig. 4) with their posterior ends decreasing in height and not overhanging the posterior edge of the postzygapophyses.