Madagascar is famous today not only for its unique biodiversity, but also for the high levels of endemism of plants and animals. Less appreciated is the fact that, in the recent past, the island had even greater biodiversity with many other endemic animals such as giant lemurs, elephant birds, pygmy hippopotami, tortoises, and crocodiles that have gone extinct within the past 2000 years. The extinction of many of these groups is thought to be the result of both human activities and environmental change. Most research has focused on the lemurs, hippopotami, and elephant birds. Other recently extinct animals, including the Malagasy horned crocodile (Voay robustus), are relatively poorly known. Madagascar’s subfossil crocodylians include two taxa: the extinct V. robustus (the Malagasy horned crocodile) and the extant Crocodylus niloticus. The latter arrived on Madagascar relatively recently and we know little about the habitat preferences, distributions and ecological interactions (if any) of either species during the Holocene.
In order to better understand the recent history of crocodylian extinction in Madagascar, we must first identify which species were present and where they were found. We present here a description of subfossil crocodylian material collected from the newly discovered subfossil site of Tsaramody (Sambaina Basin), a high-elevation wetlandenvironment. At 1655 m, it represents the highest elevation subfossil site on the island. Here we describe both cranial (e.g., premaxillary, jugal, and squamosal “horns”) and postcranial elements (e.g., osteoderms). Our research indicates that crocodile material from Tsaramody appears morphologically to belong to V. robustus, the extinct species. However, oval tuberosities on the frontal bone and a triangular extension of the squamosal bone suggest previously unrecognized variation.
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Evolutionary and phylogenetic insights from a nuclear genome sequence of the extinct, giant, “subfossil” koala lemur Megaladapis edwardsi
No endemic Madagascar animal with body mass >10 kg survived a relatively recent wave of extinction on the island. From morphological and isotopic analyses of skeletal “subfossil” remains we can reconstruct some of the biology and behavioral ecology of giant lemurs (primates; up to ∼160 kg) and other extraordinary Malagasy megafauna that survived into the past millennium. Yet, much about the evolutionary biology of these now-extinct species remains unknown, along with persistent phylogenetic uncertainty in some cases. Thankfully, despite the challenges of DNA preservation in tropical and subtropical environments, technical advances have enabled the recovery of ancient DNA from some Malagasy subfossil specimens. Here, we present a nuclear genome sequence (∼2× coverage) for one of the largest extinct lemurs, the koala lemur Megaladapis edwardsi (∼85 kg). To support the testing of key phylogenetic and evolutionary hypotheses, we also generated high-coverage nuclear genomes for two extant lemurs, Eulemur rufifrons and Lepilemur mustelinus , and we aligned these sequences with previously published genomes for three other extant lemurs and 47 nonlemur vertebrates. Our phylogenetic results confirm that Megaladapis is most closely related to the extant Lemuridae (typified in our analysis by E. rufifrons ) to the exclusion of L. mustelinus , which contradicts morphology-based phylogenies. Our evolutionary analyses identified significant convergent evolution between M. edwardsi and an extant folivore (a colobine monkey) and an herbivore (horse) in genes encoding proteins that function in plant toxin biodegradation and nutrient absorption. These results suggest that koala lemurs were highly adapted to a leaf-based diet, which may also explain their convergent craniodental morphology with the small-bodied folivore Lepilemur .
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- NSF-PAR ID:
- 10316728
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 118
- Issue:
- 26
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Most researchers believe that Madagascar’s megafauna went extinct between 2000 and 1000 years ago. Across Madagascar, fossil specimens of the island’s endemic (and now extinct) pygmy hippopotamuses, elephant birds, giant lemurs, horned crocodiles, and other vertebrates larger in body size than 10 kg commonly date to the first millennium of the Common Era (CE) or earlier; few records date to the second millennium CE. Whereas megafaunal populations appear to have crashed almost simultaneously near the end of the first millennium CE, small populations can survive in remote pockets for centuries after precipitous species decline, perhaps longer. Examining the differences in the population dynamics of declining species and other factors can help to better identify the ultimate timing of extinction. Ever since Etienne de Flacourt traveled to Madagascar in the late 1600s, Malagasy stories of large-bodied wild animals have been recorded. Many include fantastic, clearly mythical creatures, but some provide anatomical or behavioral details which are consistent with legends or even direct observations of real, albeit potentially already extinct, species (including elephant birds, hippopotamuses, and some giant lemurs). In December 1989, at 06:00 hours, one of us (BZF) witnessed a large euplerid carnivoran locally known as fosabe (big fosa) or fosa jobijoby (blackish fosa) who had entered his field tent at Montagne d’Ambre. The animal was “twice the size and much darker than the common fossa” (Freed, 1996, p. 34). The individual was black and weighed approximately 20-25 kg. Freed wrote that the animal was well known to the local people and that “many local people also reported seeing it”. The animal fits paleontologists’ expectations for Cryptoprocta spelea, a large carnivoran known from the fossil record, believed to have been extinct for at least 1000 years. In June 2020, we recorded modern accounts of the big fosa. One of us (ESN) visited villages in four different sectors (Northwest, Northeast, East, and West) of Montagne d’Ambre National Park and the Forêt d’Ambre Special Reserve to examine potential regional differences and/or similarities in the stories of this animal, and whether such accounts include mythical elements, relevant anatomical information, and/or credible recent sightings. We also recorded stories of an Endangered extant animal, the aye-aye of the genus Daubentonia (also known locally as the kakahely). Ultimately, we believe this folklore provides clues that may help elucidate the geography of decline and possible late survival of an “extinct” megafaunal animal on Madagascar.more » « less
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Abstract Objectives Variation in primate masticatory form and function has been extensively researched through both morphological and experimental studies. As a result, symphyseal fusion in different primate clades has been linked to either the recruitment of vertically directed balancing‐side muscle force, the timing and recruitment of transversely directed forces, or both. This study investigates the relationship between jaw muscle activity patterns and morphology in extant primates to make inferences about masticatory function in extinct primates, with implications for understanding the evolution of symphyseal fusion.
Materials and methods Three‐dimensional mandibular landmark data were collected for 31 extant primates and nine fossil anthropoids and subfossil lemur species. Published electromyography (EMG) data were available for nine of the extant primate species. Partial least squares analysis and phylogenetic partial least squares analysis were used to identify relationships between EMG and jaw shape data and evaluate variation in jaw morphology.
Results Primates with partial and complete symphyseal fusion exhibit shape‐function patterns associated with the wishboning motor pattern and loading regime, in contrast to shape‐function patterns of primates with unfused jaws. All fossil primates examined (except
Apidium ) exhibit jaw morphologies suggestive of the wishboning motor pattern demonstrated in living anthropoids and indriids.Discussion Partial fusion in
Catopithecus , similar to indriids and some subfossil lemurs, may be sufficient to resist, or transfer, some amounts of transversely directed balancing‐side muscle force at the symphysis, representing a transition to greater reliance on transverse jaw movement during mastication. Furthermore, possible functional convergences in physiological patterns during chewing (i.e.,Archaeolemur ) are identified. -
Paleontological and neontological systematics seek to answer evolutionary questions with different datasets. Phylogenies inferred for combined extant and extinct taxa provide novel insights into the evolutionary history of life. Primates have an extensive, diverse fossil record and molecular data for living and extinct taxa are rapidly becoming available. We used two models to infer the phylogeny and divergence times for living and fossil primates, the tip-dating (TD) and fossilized birth-death process (FBD). We collected new morphological data, especially on the living and extinct endemic lemurs of Madagascar. We combined the morphological data with published DNA sequences to infer near-complete (88% of lemurs) time-calibrated phylogenies. The results suggest that primates originated around the Cretaceous-Tertiary boundary, slightly earlier than indicated by the fossil record and later than previously inferred from molecular data alone. We infer novel relationships among extinct lemurs, and strong support for relationships that were previously unresolved. Dates inferred with TD were significantly older than those inferred with FBD, most likely related to an assumption of a uniform branching process in the TD compared to a birth-death process assumed in the FBD. This is the first study to combine morphological and DNA sequence data from extinct and extant primates to infer evolutionary relationships and divergence times, and our results shed new light on the tempo of lemur evolution and the efficacy of combined phylogenetic analyses.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2022117118
