The ‘Tully monster’ is a vertebrate

• Published in: Nature (London) 2016-04, Vol.532 (7600), p.496-499
• Main Authors: McCoy, Victoria E., Saupe, Erin E., Lamsdell, James C., Tarhan, Lidya G., McMahon, Sean, Lidgard, Scott, Mayer, Paul, Whalen, Christopher D., Soriano, Carmen, Finney, Lydia, Vogt, Stefan, Clark, Elizabeth G., Anderson, Ross P., Petermann, Holger, Locatelli, Emma R., Briggs, Derek E. G.
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; 631/181/2480; 631/181/414; 704/2151/414; Animal behavior; Animal Fins - anatomy & histology; Animals; Animals, Fossil; BASIC BIOLOGICAL SCIENCES; Biota; Cambrian; Carboniferous; Extinction, Biological; Eye - anatomy & histology; Fossils; Gastrointestinal Tract - anatomy & histology; Humanities and Social Sciences; Identification and classification; Illinois; Lampreys - classification; letter; Methods; Morphology; multidisciplinary; Notochord - anatomy & histology; Paleontology; Phylogenetics; Phylogeny; Science; Teeth; Tooth - anatomy & histology; Vertebrates; Vertebrates - anatomy & histology; Vertebrates - classification
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature16992

The Tully monster ( Tullimonstrum ), a problematic fossil from the 309–307-million-year-old Mazon Creek biota of Illinois, is shown to be not only a vertebrate but also akin to lampreys, increasing the morphological disparity of that group. Illinois' Tully monster reinterpreted Since its discovery in 1958 by Francis Tully in the approximately 300-million-year-old Mazon Creek fossil beds in Illinois, the zoological affinities of the soft-bodied animal popularly known as the Tully monster ( Tullimonstrum gregarium ) have remained mysterious. It is a remarkable looking creature, with a fish-like body featuring prominent eyes at each end of a horizontal bar, and jaws on the end of a long, jointed proboscis. Its origins have been compared variously with nemertean and polychaete worms, molluscs, conodonts and even stem-group arthropods. Now two papers in this issue identify Tullimonstrum securely as a vertebrate. Thomas Clements et al . studied the eyes and found ultrastructural details indicating homology with those of vertebrates. Victoria McCoy et al . examined more than 1,200 specimens. They re-interpret many known features, and describe and interpret many new ones: all are consistent with Tullimonstrum being a vertebrate, akin to lampreys and increasing the morphological disparity of that group. Problematic fossils, extinct taxa of enigmatic morphology that cannot be assigned to a known major group, were once a major issue in palaeontology. A long-favoured solution to the ‘problem of the problematica’ 1 , particularly the ‘weird wonders’ 2 of the Cambrian Burgess Shale, was to consider them representatives of extinct phyla. A combination of new evidence and modern approaches to phylogenetic analysis has now resolved the affinities of most of these forms. Perhaps the most notable exception is Tullimonstrum gregarium 3 , popularly known as the Tully monster, a large soft-bodied organism from the late Carboniferous Mazon Creek biota (approximately 309–307 million years ago) of Illinois, USA, which was designated the official state fossil of Illinois in 1989. Its phylogenetic position has remained uncertain and it has been compared with nemerteans 4 , 5 , polychaetes 4 , gastropods 4 , conodonts 6 , and the stem arthropod Opabinia 4 . Here we review the morphology of Tullimonstrum based on an analysis of more than 1,200 specimens. We find that the anterior proboscis ends in a buccal apparatus containing teeth, the eyes project laterally on a long rigid bar, and