Introduction

Coelacanths are a curious group of sarcopterygian fishes, represented by two extant marine species in the genus Latimeria1,2,3. This group was first known in the Early Devonian, reached their peak of taxonomic diversity during the Early Triassic, but declined after the mid-Cretaceous4,5. Coelacanths are highly significant in evolutionary biology for their unique combination of physiological and anatomical characteristics and their ability to survive four major extinction events over hundreds of millions of years6,7,8. The discovery of Latimeria once ignited a debate about how this bizarre lobe-finned fish fits into the evolution of land animals1,2. Because of evolutionary conservatism, coelacanths have long been considered one of the most morphologically conservative vertebrate groups9. However, several studies, especially those based on Triassic fossils, have shown that coelacanth body shapes are more diverse than previously thought5,10,11,12. In recent years, new taxa recovered from fossil sites worldwide continually provide valuable evidence for investigating the coelacanth evolution6,13,14,15,16,17.

Early Triassic witnessed a coelacanth radiation with at least 17 species in 12 genera reported so far18. Most of them are known from Europe (Spitsbergen, East Greenland and North Dobrogea), Africa (Madagascar and South Africa) and North America (British Columbia, Canada) with only two from China (Guangxi and Anhui)1,19,20,21,22,23,24,25,26,27. Early Triassic coelacanths from Europe and Africa have been well studied on anatomy and phylogeny, but the Chinese coelacanths remain poorly known; Sinocoelacanthus was established based on only a caudal fin26and Chaohuichthys on poorly-preserved specimens with little information on its skull27. China has substantial potential for future studies of coelacanths.

Here, we report the discovery of a new coelacanth on the basis of two specimens from the Lower Triassic marine deposits exposed in Maoshankou, He County, Anhui Province, China (Locality 1 in Fig. 1). The new finding documents the best-preserved coelacanth from the Early Triassic of China with a calcified lung discernible. Detailed comparisons indicate that the new coelacanth can be referred to the genus Whiteia, whose members were previously known from the Early Triassic of Madagascar, South Africa, East Greenland and British Columbia (Canada), and the Late Triassic of Indonesia and Texas (USA)20,21,22,23,24,25. As the first record of Whiteia from the Early Triassic of Asia, the new finding considerably extends the spatial range of the genus and provides an important addition for our understanding the evolution of this major Triassic clade of coelacanths.

Fig. 1
figure 1

Map showing four localities yielding fish nodules in Anhui and Jiangsu provinces (East China). 1, Maoshankou, He County; 2, Majiashan, Chaohu City; 3, Longtan, Nanjing City; 4, Qingshan, Jurong City. The map was created by G.-H. Xu using Baidu Map (https://map.baidu.com) and Adobe CS (https://www.adobe.com/).

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The fossil locality was situated at the northern margin of the Lower Yangtze Block28where the Lower Triassic marine deposits were well developed, including the Yinkeng, Helongshan and Nanlinghu formations from base to top. The fossil fishes were preserved in calcareous nodules embedded in black shales and mudstones from the upper part of the Helongshan Formation, and their age has been well constrained to late Smithian (~ 249 Ma), Olenekian by conodont biostratigraphic correlation29,30,31. Besides the new coelacanth, other nodular fishes from the same fossiliferous level at this locality include perleidids and parasemionotids, similar to the fossil assemblages previously known from the Chaohu, Nanjing and Jurong localities (Localities 2–4 in Fig. 1)27,31,32,33,34. Taphonomic studies suggest that these fish nodules were formed in a calm and euxinic environment with the participation of a vast array of microbes and possibly sulfur-reducing bacteria31.

Results

Systematic palaeontology

Osteichthyes Huxley, 1880.

Sarcopterygii Romer, 1955.

Actinistia Cope, 1871.

Coelacanthiformes Huxley, 1861.

Whiteiidae Schultze, 1993.

Whiteia Moy-Thomas, 193520.

Whiteia anniae Xu, Dai, Tan, Yuan, Sun, Liao, Geng et Song sp. nov.

Etymology. The specific epithet honors the British fossil hunter Mary Anning and her Chinese fan Anni Dai, whose family contributes to the collection of fossils described here.

Holotype. CHU 2016 (Fig. 2). A laterally compressed specimen with the anal fin and caudal missing, stored in the fossil collection of Chaohu University (CHU).

Fig. 2
figure 2

Whiteia anniae sp. nov. in right lateral view, Holotype (CHU 2016). (a), Whole specimen. (b), closeup of the calcified lung (indicated by lower arrows) and lateral line (indicated by upper arrows). (c), a scale near the head. (d), anterior tips of jaws with arrows indicating the fangs in anterior coronoids. (e), denticles on the last ray of the anterior dorsal fin.

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Paratype. CHU 2017 (Fig. 3). A relatively complete specimen with the second dorsal fin, pectoral and pelvic fins missing.

Fig. 3
figure 3

Whiteia anniae sp. nov., Paratype (CHU 2017). Photo (a) and line-drawing (b). a.Pa, anterior parietal; cau.f, caudal fin; Cb, ceratobranchial; Ch, ceratohyal; Cl, cleithrum; Cla, clavicle; D1.b, basal plate of the anterior dorsal fin; D1.f, anterior dorsal fin; D2.b, basal plate of the posterior dorsal fin; Ecl, extracleithrum; Gu, gular; h.a + s, haemal arch plus spine; n.a + s, neural arch plus spine; Op, opercle; Ppa, postparietal; p.Pa, posterior parietal; Ps, parasphenoid; Ra, radial; sup.cau.f.l, supplementary caudal fin lobe; Sy, symplectic; Uhy, urohyal.

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Locality and horizon. He County, Anhui Province; Helongshan Formation, Smithian, Olenekian, Early Triassic29,30.

Diagnosis. A large species of Whiteia characterized by the following set of characters (autapomorphies, those unique among Whiteia, identified with an asterisk): presence of six enlarged conical teeth on premaxilla; presence of coronoid fangs (*); presence of contact of first supraorbital with posterior portion of anterior parietal; anterior extremity of preorbital at level of anterior margin of anterior parietal (*); trapezoidal opercle with rounded anteroventral corner; 49 neural arches and 22 haemal arches in vertebral column; eight rays in anterior dorsal fin; pointed denticles associated with rays of anterior dorsal fin; 14 rays and 15 radials, and 12 rays and 13 radials respectively in dorsal and ventral lobes of caudal fin (*); and scale ornamentation consisting of about 20 elongate ridges converging midline posteriorly (*).

Description. The type specimens show that Whiteia anniae was notably larger than other named species of the genus at its age. The holotype, although incomplete, has a head length of 106 mm (from the rostral tip to the posterior end of the opercle) and a preserved length of 294 mm from the rostral tip to the 43th neural arch (Fig. 2a). The paratype is relatively complete, having a head length of ~ 80 mm, a standard length of 300 mm, and a total length of ~ 350 mm (a preserved length of 340 mm; Fig. 3). According to the ratio of the paratype, the holotype is estimated to have a standard length of ~ 400 mm and a total body length (TL) of ~ 460 mm. However, if Toriño et al.’s model35 of body size estimation based on the gular plate is applied, the holotype has an estimated TL of 417–425 mm (see Discussion below). In comparison with non-Whiteia coelacanths, W. anniae is larger than most of other coelacanths in the Early Triassic (e.g., Chaohuichthys27, Laugia and Piveteauia23) whose total lengths range from 140 mm to 303 mm, with the exception of 1300 mm long Rebellatrix divaricerca10.

The skull roof of Whiteia anniae is divided into the parietonasal shield and the postparietal shield (Fig. 4), delimited by an intracranial joint as commonly in other coelacanths1. The parietonasal shield is notably longer than the postparietal shield; measured from the holotype, the former is 51 mm and the latter 27 mm. There are two pairs of parietals as in many other coelacanths; the anterior is similar to the posterior in length. By contrast, only one pair is present in some coelacanths (e.g., Laugia, Axelia and Wimania1,8). Three nasals are located anterior to the anterior parietal on each side of skull. They are rectangular or trapezoidal, gradually reduced in length anteriorly. There are five trapezoidal or rectangular supraorbtials on the right side. Among them, the first (anteriormost) is the largest, which medially contacts the posterior half of the anterior parietal, and others are relatively small, flanking the posterior parietal. The postparietal is trapezoidal with straight anterior and posterior margins. It is slightly widened at the posterior third portion of the bone, where it contacts the supratemporal laterally. The supratemporal is trapezoidal, bearing a blunt descending process. Posterior to the postparietal, two lateral extrascapulars and a possible medial one are discernible at the right side of the skull (Fig. 4). They are small and plate-like bones. Some small tubercles are discernible on the external surfaces of nasals, but other elements on the skull roof are nearly smooth.

Fig. 4
figure 4

Skull and pectoral girdle of Whiteia anniae sp. nov., Holotype (CHU 2016). Acl, anocleithrum; Ang, angular; a.Pa, anterior parietal; Apal, autopalatine; Cl, cleithrum; Cla, clavicle; Co, coronoid; D, dentary; Dpl, dermopalatine; Ecl, extracleithrum; Ecpt, ectopterygoid; Ext.l, lateral extrascapular; Ext.m, median extrascapular; Gu, gular; Icla, interclavicle; L.j, lachrymojugal; L. r, lateral rostral; Mm, mentomeckelian; Na, nasal; nos.a, anterior nostril; Op, opercle; Part, prearticular; p.Co, principal coronoid; Pmx, premaxilla; Po, postorbital; Pop, preopercle; Ppa, postparietal; p.Pa, posterior parietal; Preo, preorbital; Ps, parasphenoid; Pt, pterygoid; Rart, retroarticular; Ro, rostral; Scc, scapulocoracoid; So, supraorbital; S.o, sclerotic ossicles; Sop, subopercle; Sp, spiracular; Spl, splenial; Sq, squamosal; Stt, supratemporal; Te, tectal.

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The snout region of Whiteia anniae is relatively long with the preorbital length (35 mm in the holotype) being about one-third of the skull length (Fig. 4). This is similar to the conditions in some coelacanths (e.g., Chinlea, Guizhoucoelacanthus36 and W. woodwardi1) but different from those short-snouted forms (e.g., Axelia, Gavinia and Mawsonia1). Just lateral to the parietonasal shield is the tectal series, which includes four rectangular elements (Fig. 4). The last tectal is the longest, and the first the shortest. The preorbital is oval-shaped and contributes little of the anterior orbital margin. The anterior tip of the bone is located at the level of anterior margin of anterior parietal. The elongate lateral rostral extends below the tectal series and contacting the rostral and premaxilla anteriorly. Both the rostral and possibly paired premaxillae form the anterior tip of the skull. They are plate-like; the rostral is larger than the premaxilla. There are six enlarged conical teeth along the oral margin of the premaxilla. The anterior nostril is located between the lateral rostral and premaxilla as in W. woodwardi, but the posterior nostril is hard to identify.

The cheek bones and opercle are well-preserved. However, most of the lachrymojugal is missing with only a short anterior portion preserved below the preorbital, and its outline is tentatively reconstructed in accordance with that in Whiteia woodwardi (Fig. 5a, b). A few sclerotic ossicles are discernible near the orbit margin, and they are small and quadrangular. The postorbital and squamosal are trapezoidal, and the former is smaller than the latter. The anterior margins of both bones are located at the level of the intracranial joint. The preopercle, positioned just below the squamosal, is subcircular and slightly tapers anteriorly. Similar to W. woodwardi, the small triangular spiracular and trapezoidal subopercle are positioned dorsally and ventrally in the cheek region, respectively. The opercle is large and trapezoidal with rounded corners. Some small tubercles are discernible on the external surfaces of the squamosal, preopercle and opercle. Moreover, the opercle bears fine striae which radiate posteriorly and ventrally on the surface of its posterior portion.

Fig. 5
figure 5

(modified from refs1,8). (c), reconstruction of head and pectoral girdle of W. anniae sp. nov. The Early Triassic palaeogeographical map was adopted from ref42.

Paleogeographical distribution of Whiteia in the Early Triassic and reconstructions of head and pectoral girdle in two selected species. (a), 1, Whiteia woodwardi, W. tuberculata, and W. uyenoteruyai, Madagascar; 2, W. africana, South Africa; 3, W. gigantea, Texas (USA); 4, Whiteia sp., British Columbia (Canada); 5, W. neilseni, East Greenland; 6, W. anniae sp. nov., Anhui, China. (b), reconstruction of head and pectoral girdle of W. woodwardi.

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The palatoquadrate complex of Whiteia anniae is partly exposed. It would comprise the entopterygoid, quadrate and metapterygoid as in other coelacanths, but the sutures between them are obscure because of taphonomic compression. Most of the metapterygoid is laterally covered by the postorbital except for its dorsal process that articulates with the braincase. Additionally, the quadrate condyle is partly exposed between the preopercle and the glenoid fossa of the lower jaw. The autopalatine is well-ossified and triangular in shape, medially contacting the anterior portion of the palatoquadrate complex. Anteriorly, two dermopalatines are present; both are small and toothed. In the ethmoid region, a pair of small vomers are discernable. The right vomer is twice as long as the anterior dermopalatine, bearing 13 small villiform teeth along its oral margin (Figs. 2d and 4). The parasphenoid is discernible laterally through the orbit in the holotype and dorsally in the paratype. It is relatively broad throughout its length, and slightly expanded anteriorly. Some small teeth are present on the palatal surface at most of its orbital portion.

The branchial apparatus is only discernible from the paratype (Fig. 3), including five long and curved ceratobranchials, a partly exposed ceratohyal and a urohyal. No dentition was preserved associated with the ceratobranchials. The urohyal is dorsoventrally flattened, narrow anteriorly and expanded posteriorly with bifid anterior and posterior extremities. A urohyal with a forked anterior extremity was otherwise known in Ticinepomis ducanensis16, but the extant Latimeria and many other coelacanths (including W. woodwardi) have a urohyal with a nearly straight anterior margin1.

The lower jaw of Whiteia anniae is well preserved laterally (Fig. 4). The angular is the largest element of the lower jaw with a prominent coronoid expansion midway along its length. The dentary is elongate and embayed posteriorly, being about one third of the mandibular length. It bears a short hook-shaped process, the distal part of which was broken away during preparation in the holotype. The dentary tapers posteriorly, having a long overlapping suture with the angular. The splenial is elongate, slightly angled downwards. A small triangular element located between the anterior portions of the dentary and splenial likely represents the mentomeckelian. Two elongate splenial sensory pores and a single large dentary sensory pore are discernible laterally, but the sensory pores on the angular are not exposed because of the overlapping of the gular. As in most coelacanths (except Axelrodichthys37 and most specimens of Mawsonia15,38), the subcircular principal coronoid of W. annia is not suture to the angular. The anterior margin of the principal coronoid is situated at level of the anterior orbital margin. Several small, toothed plate-like bones preserved between the right and left dentaries reasonably represent the anterior series of coronoids according their shape and position. Besides tiny denticles on their oral margin, one or two fangs are present on each of anterior coronoids. The partly exposed prearticular is large and elongate, contacting the dentary and angular laterally. The retroarticular is small, articulating with the angular at the posterior extremity of the lower jaw. The articular is hardly discernible. The large and elongate gulars ventrally floor the intermandibular space and do not extend behind the jaw rami. Each is 84% of the mandibular length. Small tubercles are present on the external surfaces of the angular, and other bones are nearly smooth.

The pectoral girdle of Whiteia anniae is curved and boomerang shaped, with its components (anocleithrum, cleithrum, extracleithrum, clavicle and scapulocoracoid) well-preserved in the holotype (Fig. 4). The anocleithrum is relatively small and tapers anterodorsally with its ventral portion overlapped by the cleithrum. The cleithrum is deep and curved, having a slightly expanded dorsal portion. The extracleithrum is plate-like, being about one-third of the length of the whole girdle. The clavicle is curved and as deep as the extracleithrum, bearing a long dorsal process that sutures with the cleithrum posteriorly. The interclavicle is elongate and curved, half the length of the clavicle, similar to that in W. woodwardi. Additionally, a small scapulocoracoid is positioned near the junction of the cleithrum with the extracleithrum.

The pectoral fin web consists of 25 rays; among them, the first four rays are short and unsegmented, and others are segmented distally (Fig. 2a). The pelvic fin web consists of 27 segmented rays. The complete morphology of basal plates for the paired fins remains unknown because they are only incompletely exposed in the holotype.

The anterior dorsal fin of Whiteia anniae bears eight long, distally segmented and unbranched rays (Figs. 2a and 3). Additionally, there is a very short unsegmented ray preceding the base of the first segmented ray. Several denticles can be discernible near the anterior margin of the first segmented ray and the posterior margin of posterior rays (Figs. 2e and 3), although these denticles were easily broken away during preparation. The basal plate is large and approximately triangular with a straight ventral margin and convex anterior and posterior margins. A ridge originates from the anteroventral corner, extends posterodorsally for a length, and ends at the level of the dorsal corner of the bone. The posterior dorsal fin bears about 17 long and distally segmented rays, preceded by three short unsegmented rays. The basal plate for the posterior dorsal fin is composed of a plate-like distal part and a stout anteroventral process (Fig. 3). The anal fin is missing.

The caudal fin is developed as nearly symmetrical dorsal and ventral lobes and a middle supplementary lobe (Fig. 3). There are 14 rays and 15 radials in the dorsal lobe, and 12 rays and 13 radials in the ventral lobe. Two anterior radials and one radial respectively in the dorsal and ventral lobes do not support any rays; they are relatively short and taper distally. The other radials are longer and more expanded in their extremities. The anteriormost ray in each lobe is relatively short and unsegmented, and other rays are distally segmented. The supplementary caudal lobe, represented by four slender and segmented rays, is enclosed in the caudal fin but the tip is missing.

The vertebral column of Whiteia anniae is well exposed in the paratype (Fig. 3). It is composed of 49 neural arches and 22 haemal arches. The anterior nine neural spines are relatively short below and in front of the anterior dorsal fin, and the remaining spines are longer. The haemal arches are absent in the anterior part of the axis and they first appear below the center of the basal plate for the posterior dorsal fin. The haemal spines increase in length posteriorly, reach their great length in the support of the anterior part of the caudal fin, and then gradually reduce towards the last one. The pleural ribs are absent, and they are probably not ossified.

The squamation can be observed in the holotype. The ornament on the scales consists of about twenty elongate ridges which converge midline posteriorly (Fig. 2c). This ornament is different from the conditions in other Whiteia species but somewhat similar to those in Caridosuctor populosum and Rhabdoderma ardrossense1.

Additionally, the exceptional preservation allows the identification of a calcified lung in the holotype, which is indicated by an oval organ surrounded by some ossified plates in the abdominal cavity (Fig. 2b). The posterior plates end at the level of the 22th neural arch. Previous studies39 suggest that these plates most likely functioned in volumetric regulation and protection of the lung against hydrostatic pressure. Within Whiteia, a calcified lung is otherwise known in W. uyenoteruyai24 but it is notably longer than that in W. anniae. It is unclear if the difference is caused by an artifact of preservation.

Phylogenetic analysis

To assess the phylogenetic affinities of Whiteia anniae, we incorporated it into a dataset from a previous study8 (see Methods and Supplementary Information). Our phylogenetic analysis resulted in 216 most parsimonious trees (tree length = 347 steps, consistency index = 0.4467, retention index = 0.7130), a strict consensus of which is presented in Fig. 6. W. anniae is recovered sister to W. woodwardi, and both form the sister group to the clade Garnbergia-Guizhoucoelacanthus within the Whiteiidae among the Coelacanthiformes. The whole topology is consistent with the previous hypothesis8 in placing Miguashaiidae, Diplocercidae and Hadronectoridae at basal positions of the Actinistia, followed successively by Sassenuia, Rhabdodermatidae and Coelacanthiformes. A small inconsistency involves the position of Whiteiidae relative to Axeliidae within the Coelacanthiformes: results of our phylogenetic analysis recover Whiteiidae as the sister group to Latimerioidei (including Mawsoniidae and Latimeriidae), contrasting the previous hypothesis8 that instead recovered it sister to the clade Axeliidae-Latimerioidei. This partly reflects that the present topology on the coelacanth phylogeny remains unstable, as also indicated by the lower Bremer supports at many nodes that are one step away from collapse. Additionally, we incorporated it into the dataset from another recent analysis5and the analysis recovered W. anniae as the sister taxon to W. woodwardi as well (Supplementary Information). We notice that the positions of Whiteiidae were affected by differential character and taxon inclusions in different analyses and the monophyly of this family was even challenged by some analyses5,7,11,13,25. Nevertheless, a further comprehensive analysis of whiteiid relationships is out of scope of this paper.

Fig. 6
figure 6

Time-scaled phylogeny of Actinistia. The strict consensus of 216 most parsimonious trees (tree length = 347 steps, consistency index = 0.4467). Digits at nodes indicate Bremer decay indices larger 1. The periods are in million years, and the figure frame and time-calibration of phylogeny are from ref8.

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Discussion

The new coelacanth is assignable to Whiteia because it possesses the following diagnostic features of the genus1: a relatively elongated snout with the preorbital length greater than one-third the length of the skull roof; a short and broad postparietal shield approximately half the length of the relatively narrow parietonasal shield; three nasals followed by two parietals of similar length; presence of an ovoid preorbital, multiple tectals and supraorbitals; a particularly large anteriormost supraorbital nearly meeting the lachrymojugal and excluding the preorbital from the orbital margin; a premaxilla contributing to the anterior nostril; presence of a spiracular and subopercle; tubercle ornament variously developed only upon the cheek bones, opercular bones and the angular (absent or very sparse upon the skull roofing bones); and presence of a simple triangular plate supporting the anterior dorsal fin with a single anteroventrally directed strengthening ridge. Although most of these features are not uniquely derived, this combination is only known in Whiteia. Notably, a ventrally pointed opercle was once proposed diagnostic for Whiteia, but this feature is not shared by the recently described species of the genus. The Late Triassic W. oishii14as well as W. anniae described herein, has an opercle with a rounded anteroventral corner. Additionally, a ventrally pointed opercle is otherwise present in many non-Whiteia coelacanths, e.g., Coelacanthus, Diplurus and Macropomoides1and consequently has limited significance in taxonomic identification. As such, we consider that this feature does not hamper the assignment of the new coelacanth into Whiteia.

Within Whiteia, W. anniae is easily distinguished from other species by several features, e.g., presence of fangs on anterior coronoids (vs. absent in other species), presence of contact of the first supraorbital with the posterior portion of anterior parietal (vs. first supraorbital more anteriorly located in other species), location of anterior extremity of preorbital at level of anterior margin of anterior parietal (vs. preorbital more anteriorly located in other species) (see Fig. 5); 14 and 12 rays respectively in dorsal and ventral lobes of the caudal fin (vs. slightly more caudal rays in other species; see Table 1); and squamation ornamentation consisting of elongate ridges converging midline posteriorly (vs. parallel ridges or tubercles in other species). Moreover, the opercle ornamentation and the denticles on the first dorsal fin are also useful in distinguishing W. anniae from some other species of Whiteia (Table 1).

Table 1 Character comparisons within Whiteia.
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As the first record of Whiteia from the Early Triassic of Asia, the new finding not only adds the morphological diversity of the genus but also considerably extends the spatial range of this family at this epoch (Fig. 5). Previously, at least seven species were referred to Whiteia, including W. woodwardi, W. tuberculata and W. uyenoteruyai from the Middle Sakamena Group of Madagascar1,20,24, W. africana (formerly W. africanus) from the Beaufort Beds of South Africa, W. neilseni from the Wordie Creek Formation of East Greenland1, Whiteia sp. from the Sulphur Mountain Formation of British Columbia (Canada)21, W. gigantea (formerly W. giganteus) from the Carnian Dockum Group of Texas (USA)25 and W. oishii from the Upper Triassic (Carnian to Norian) of West Timor (Indonesia)14. Most species of Whiteia are from the Early Triassic, except the last two species who are Late Triassic in age. The recovery of W. anniae further adds the taxonomic diversify of the genus in the Early Triassic and represents the oldest record of the Whiteiidae in Asia. The previously oldest member of the Whiteiidae in this continent was represented by Guizhoucoelacanthus from the late Middle to Late Triassic (240-230 Ma) of Southwest China36. The new finding extends the geological range of Asian whiteiids back to the late Smithian (~ 249 Ma), predating the previously oldest record of this family in Asia by nine million years.

The recovery of Whiteia anniae documents the largest, convincing species of the genus known in the Early Triassic so far. Recently, allometric equations are proposed by Toriño et al.35 for the coelacanth body size estimation based on the length of the gular plate. The relatively complete preservation of the paratype of W. anniae (Fig. 3) provides a good example testing these equations. The gular is 48 mm in the paratype. If Toriño et al.’s allometric Eq.35 are applied, the total length of the paratype would fall between 322 (OLS) and 325 mm (RMA). This estimated length is shorter than the preserved length (340 mm; Fig. 3), and undoubtedly shorter than the real length of the paratype. As for the holotype with a gular length of 62 mm (Fig. 2), its estimated TL would fall between 417 (OLS) to 425 mm (RMA) if Toriño et al.’s allometric equations are applied. There is a deviation between the estimated TL based on allometric model (~ 420 mm) and that resulted from the linear ratio (~ 460 mm). To be on the safe side, we consider that W. anniae has an estimated TL of at least 420 mm. This is larger than almost all other Early Triassic coelacanths (e.g., Chaohuichthys27, Laugia, Piveteauia and W. woodwardi1; except Rebellatrix10) whose total lengths range from 140 mm to 303 mm. The previously reported Whiteia species were generally small with a total length of 115 mm to 270 mm in the Early Triassic, and a small and slender body form was once considered characteristic of the genus1. A skull referable to Whiteia sp. from British Columbia likely indicates an individual approaching 1000 mm, but it has not been named and lacks a formal analysis because of incomplete preservation21. Recently, the recovery of W. gigantea (estimated TL > 1000 mm) from Texas reveals an episode of large body size acquisition of the genus in the Late Triassic of North America25. Body size is often used as a proxy for analyzing morphological disparity35,40. Our recovery of W. anniae from China provides an interesting example that bridges the small species of Whiteia from Europe and Africa and those much larger relatives from North America in body size.

Methods

Phylogenetic analysis

In order to assess the phylogenetic position of Whiteia anniae within the Actinistia, we incorporated it into a matrix of ref8. Onychodus jandermarrai was selected for out-group comparison, following the previous analysis8. The maximum parsimony analyses were performed with a heuristic search in PAUP* (v. 4.0a169)41 using 800 random addition sequence replicates, holding five trees at each step, with the tree bisection and reconnection (TBR) strategy enabled and maxtrees set to automatically increase by 100. In addition, we incorporated W. anniae into the matrix of ref5. for an additional analysis, and the results are presented in the Supplementary Information for further comparison.