An ammonite trapped in Burmese amber Tingting Yua,b,c,1, Richard Kellya,d,e,1, Lin Mua,1, Andrew Rosse, Jim Kennedyf,g, Pierre Brolyh, Fangyuan Xiai, Haichun Zhanga,b, Bo Wanga,b,j,2, and David Dilcherk,2 aState Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China; bCAS Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, Nanjing 210008, China; cSchool of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China; dSchool of Earth Sciences, University of Bristol, Bristol BS8 1TQ, United Kingdom; eDepartment of Natural Sciences, National Museum of Scotland, Edinburgh EH1 1JF, United Kingdom; fOxford University Museum of Natural History, Oxford OX1 3PW, United Kingdom; gDepartment of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom; hPrivate address, 59840 Lompret, France; iLingpoge Amber Museum, Shanghai 201108, China; jKey Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China; and kDepartment of Geology and Atmospheric Science, Indiana University, Bloomington, IN 47405 Contributed by David Dilcher, February 27, 2019 (sent for review December 13, 2018; reviewed by Phillip Barden and Enrique Peñalver Mollá) Amber is fossilized tree resin, and inclusions usually comprise (at least 40 individuals) of arthropods in this amber sample that live terrestrial and, rarely, aquatic organisms. Marine fossils are ex- today in both terrestrial and marine habitats. Of the terrestrial tremely rare in Cretaceous and Cenozoic ambers. Here, we report a fauna, Acari (mites) are the most abundant, with 23 specimens; also record of an ammonite with marine gastropods, intertidal isopods, present are Araneae (spiders), Diplopoda (millipedes), and repre- and diverse terrestrial arthropods as syninclusions in mid-Cretaceous sentatives of the insect orders Blattodea (cockroaches), Coleoptera Burmese amber. We used X-ray–microcomputed tomography (CT) to (beetles), Diptera (true flies), and Hymenoptera (wasps). The ar- obtain high-resolution 3D images of the ammonite, including its su- thropod assemblage consists mostly of forest floor-dwelling taxa, tures, which are diagnostically important for ammonites. The am- and living representatives are generally associated with leaf litter or monite is a juvenile Puzosia (Bhimaites) and provides supporting the top layers of soil. There are several isopods preserved which are evidence for a Late Albian–Early Cenomanian age of the amber. consistent with littoral or supralittoral taxa. In addition to the There is a diverse assemblage (at least 40 individuals) of arthropods ammonite itself, four definitively marine gastropod shells and one in this amber sample from both terrestrial and marine habitats, putatively marine isopod are present. including Isopoda, Acari (mites), Araneae (spiders), Diplopoda EVOLUTION (millipedes), and representatives of the insect orders Blattodea Ammonite. The ammonite is a juvenile (the adapertural septa are (cockroaches), Coleoptera (beetles), Diptera (true flies), and Hyme- not crowded), has a maximum preserved diameter of 12 mm, and noptera (wasps). The incomplete preservation and lack of soft body appears to retain the original aragonitic shell, on the basis of its of the ammonite and marine gastropods suggest that they were appearance in reflected light (Fig. 2A). It is composed in part by dead and underwent abrasion on the seashore before entombment. the body chamber, but the apertural part is damaged, as revealed It is most likely that the resin fell to the beach from coastal trees, by the survival of a 60° sector of the umbilical wall extending picking up terrestrial arthropods and beach shells and, exceptionally, beyond the fragment of the inner flanks of the shell (Fig. 2). surviving the high-energy beach environment to be preserved as Coiling is moderately involute, with ∼64% of the previous whorl amber. Our findings not only represent a record of an ammonite in covered. The small, shallow umbilicus comprises 18% of the amber but also provide insights into the taphonomy of amber and diameter, the low umbilical wall is very weakly convex, and the the paleoecology of Cretaceous amber forests. umbilical shoulder is broadly rounded. The whorl section is amber | ammonite | fossil | paleoecology | taphonomy Significance mber provides a unique mode of preservation for organisms, Aand when inclusions are present they are usually 3D fossils Aquatic organisms are rarely found in amber, but when they of terrestrial plants, microorganisms, arthropods, and even verte- occur they provide invaluable evidence for the better un- brate remains (1–3). Amber deposits are therefore considered to be derstanding of amber taphonomy and past ecosystems. We report an ammonite and several marine gastropods alongside a exceptional Lagerstätten, providing unique windows into past eco- mixed assemblage of intertidal and terrestrial forest floor or- systems (4–6). Given that amber is formed by the fossilization of ganisms in mid-Cretaceous Burmese amber. Our discovery in- terrestrial plant resins, the capture of marine inclusions may be dicates that the Burmese amber forest was living near a considered extremely rare. However, some recent findings of ma- dynamic and shifting coastal environment. The ammonite also rine and freshwater fossils, particularly, microfossils such as dia- provides supporting evidence for the age of the amber, which toms, radiolarians, ostracods, and copepods, have provided fresh is still debated, and represents a rare example of dating using – insights into amber taphonomy (7 12). fossils present inside the amber. Burmese amber (from northern Myanmar) contains the most diverse biota of all known Cretaceous ambers (13, 14). Over the Author contributions: B.W. and D.D. designed research; T.Y., R.K., L.M., A.R., J.K., and last 100 years, and particularly in the past two decades, Burmese B.W. performed research; T.Y. and F.X. contributed new reagents/analytic tools; T.Y., R.K., amber has received worldwide scientific interest; more than 500 L.M., A.R., J.K., P.B., H.Z., B.W., and D.D. analyzed data; and T.Y., R.K., L.M., A.R., J.K., B.W., and D.D. wrote the paper. families of invertebrates, vertebrates, protists, plants, and fungi Reviewers: P.B., New Jersey Institute of Technology; and E.P.M., Instituto Geológico y have been reported (15). Here, we provide an account of an Minero de España. exceptional piece of amber that preserves a unique assemblage The authors declare no conflict of interest. of marine macrofossils, alongside intertidal, fully terrestrial, and This open access article is distributed under Creative Commons Attribution License 4.0 possibly freshwater aquatic arthropods. (CC BY). 1T.Y., R.K., and L.M. contributed equally to this work. Results 2To whom correspondence may be addressed. Email: [email protected] or dilcher@ The ammonite-bearing piece of amber (BA18100) was obtained indiana.edu. from an amber mine located near Noije Bum Village, Tanaing This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. Town (ref. 16 and Fig. 1). It is 33 mm long, 9.5 mm wide, and 1073/pnas.1821292116/-/DCSupplemental. 29 mm high, and its weight is 6.08 g. There is a diverse assemblage www.pnas.org/cgi/doi/10.1073/pnas.1821292116 PNAS Latest Articles | 1of6 Downloaded by guest on September 28, 2021 Middle East, KwaZulu-Natal (South Africa), Mozambique, Madagascar, northern Pakistan, Australia, Patagonia, and Antarctica. There are similarities with juveniles of the Lower Albian Beudanticeras caseyi Collignon (ref. 19, p. 72, pl. 267, fig. 1165; holotype refigured by ref. 20, text-fig. 3j, k), known from Mada- gascar and northern KwaZulu-Natal (South Africa), and compara- bly sized juveniles of the Tunisian upper Lower Albian Beudanticeras dupinianum var. africana (ref. 21, p. 133, pl. 5, figs. 16, 17; text-fig. 49), as figured by Latil (ref. 22, pl. 3, figs. 1–19). These species, however, do not develop the low folds and undulations of the pre- sent specimen, and Beudanticeras is restricted to the Albian. Among the Puzosiinae, there are similarities with Puzosia (Bhimaites) Matsumoto (23), which ranges from the Upper Albian to the Upper Cenomanian and is known from western Europe, North Africa, Angola, KwaZulu-Natal (South Africa), Madagascar, South India, Japan, and Venezuela. The falcoid course of the ornament, which matches our specimen, is seen in several representatives of the genus, for example, the Upper Albian Puzosia (Bhimaites) pinguis (24) illustrated by Kennedy and Klinger (ref. 25, text-fig. 12a–g). A feature of Puzosia (Bhimaites) is the development of constrictions on the internal mold; their position is marked on the shell surface by much weaker depressions and associated collar ribs. These are very weakly expressed or absent in specimens com- parable in size to the present specimen [see, for example, the somewhat larger (30 mm diameter) individual of Bhimaites stoliczkai (26) figured by Renz (ref. 27, pl. 8, fig. 2)]; this species ranges from the Upper Albian to Lower Cenomanian. To conclude, features of the ammonite preserved most strongly suggest a juvenile Puzosia (Bhimaites), a subgenus that first appeared in the Upper Albian and ranged through the Cenomanian. Isopods. There are four isopod specimens in the amber (Fig. 3 A– C) and a further three specimens, which cannot be determined but may also be isopods. The first isopod (Fig. 3A) is consistent with terrestrial isopods in body shape: the eyes appear to be reduced, although this is not entirely clear, and there are six to Fig. 1. Geological and paleogeographic maps of Burmese amber. (A) Geo- seven pereonite segments with all pereopods ambulatory. The logical map showing the position of Burmese amber in Hukawng Valley, form of the uropods, if present, is not entirely clear, which is northern Myanmar. (B) Paleogeographic map showing the position (red unfortunate, as this is a key character for distinguishing marine triangle) of Burmese amber site during Late Albian (14, 17).