Mosasaurus cf. lemonnieri Dollo, 1889c

Machalski, Marcin, Jagt, John W. M., Dortangs, Rudi W., Mulder, Eric W. A. & Radwański, Andrzej, 2003, Campanian and Maastrichtian mosasaurid reptiles from central Poland, Acta Palaeontologica Polonica 48 (3), pp. 397-408 : 403-405

Mosasaurus cf. lemonnieri Dollo, 1889c

Fig. 7 .

Material.—Three tooth crowns ZPAL R. 9/1, ZPAL R. 9/2, andZPALR.9/5fromtheupperUpperMaastrichtianopoka at Nasiłów. Comparative material from the Maastrichtian type area includes NHMM 001463 , NHMM 1997269 , NHMM 1997299 , and NHMM 1997304 .

Description.—Best preserved is ZPAL R. 9/1 ( Fig. 7B ), which is bicarinate and measures 30 mm in height, and 14.7 mm in width (at the base). In cross section the crown is ellipticalwiththelingualsurfacemoreinflated.Bothanterior and posterior carinae are well developed, with minute serrationsvisibleonlydistally.Thecrownhasaslightposterior recurvature, but more pronounced lingual recurvature. The buccal surface shows four facets of unequal width, the lingual surface 7. The facets are separated by distinct ridges orstriae(resultingintheirslightconcavity) and reach tojust above mid−height of the crown.

SpecimensZPALR.9/2( Fig.7A )andZPALR.9/5( Fig. 7C ), although fragmentary, reveal the same morphology. ZPAL R. 9/5 shows traces of beading proximally.

Discussion.— Mosasaurus lemonnieri seems to be closely related to M. hoffmanni ( Lingham−Soliar 2000) . Its teeth are usually more slender and smaller than those of adult M. hoffmanni .Toothfacetsin M. lemonnieri areseparatedbydistinct ridges (striae sensu Lingham−Soliar 2000). As a result, the facets are slightly concave rather than flat or slightly convexasin M. hoffmanni ( Meijer1984) .Moreover,thefacetson both sides of the crown are approximately of the same width, whereas in M. hoffmanni they are much wider on the buccal side( Dollo1924; Meijer1984;Kuypersetal.1998).Itshould also be noted that some specimens of M. lemonnieri from the Mons Basin (especially IRScNB 3109) reveal crowns with a near−smooth surface ( Kuypers et al. 1998). These, however, are absent in the Polish material under discussion.

Stratigraphic and geographic range.—Theoriginalmaterial of M. lemonnieri is from the lower Lower Maastrichtian Belemnella obtusa Zone of the Mons Basin, southern Belgium. In the Maastrichtian type area, the lowermost occurrenceofthespeciesisatthebaseoftheValkenburgMember (MaastrichtFormation,lowerUpperMaastrichtian Belemnitella junior Zone ). It is not common, and does not range up into the Meerssen Member, let alone to the K/Pg boundary ( Mulder et al. 1998).

Mosasaurus lemonnieri was much less widely distributed than M. hoffmanni . There are no well−documented records of this species outside Belgium and the Netherlands. Tooth crownsfromtheMaastrichtianofZaire( Congo)referredtoas cf. Mosasaurus lemonnieri by Lingham−Soliar (1994b: fig. 1g –j)differinhavingapproximatelysixbuccaland12–14lingual striae, and in lacking the lingual recurvature of the crowns,typicalofthespecies.TheyresemblespecimenMKD. MP−18fromtheupperUpperMaastrichtianofNasiłówherein referred to as Plioplatecarpinae sp. B (see below). However, some of the tooth crowns in the type series of Mosasaurus beaugei Arambourg, 1952 (pl. 39: 13–21) from the MaastrichtianofMoroccomayberelated,especiallythemorelaterally compressed ones showing a slight lingual recurvature.

“ Mosasaurus (Leiodon) cfr. anceps ” sensu Arambourg (1952)

Fig. 8 .

Material.—A single tooth ZPAL R.9/3 and a tooth crown ZPAL R. 9/4 from the upper Upper Maastrichtian opoka at Nasiłów. Comparative material from the Maastrichtian type area includes NHMM 007129 .

Description.—Specimen ZPAL R. 9/3, a lateral tooth, measures 85.8 mm in height (inclusive of root), and shows well−developed anterior and posterior carinae, both with minute serrations ( Fig. 8A ). In cross section it is elliptical, with buccal and lingual surfaces subequal, the latter more broadlyrounded.Facettingisnotwelldeveloped,butismore clearly seen on thelingualsurface. The crown isfaintlyposteriorly recurved, and more strongly so lingually. Enamel beading is present, but poorly developed.

Specimen ZPAL R. 9/4 ( Fig. 8B ) is 45 mm in height and has a subcircular cross section, with a more broadly rounded lingualsurface, well−developed anterior and posterior carinae with minute serrations, faint facets on both surfaces, and depressed areas parallel to both carinae, along the entire crown height. Enamel beading is well developed.

Discussion.—Thereisagoodmatchbetweenthesespecimens andmaterialfromtheMaastrichtianofMoroccoreferredtoas Mosasaurus (Leiodon) cfr. anceps byArambourg(1952:279, pl. 38;pl. 39:8–11). There isalso a good match with a single toothNHMM007129fromtheMaastrichtiantypearea,illustrated by Kuypers et al. 1998: pl. 3: 3, 4, and ascribed to M. hoffmanni . All these teeth have subequal buccal and lingual surfaces (with buccal surfaces slightly more inflated), sharp and excavated cutting edges, weakly developed facets (better developed in the Polish material than in that from Morocco) andmoreorlessclearlydevelopedbeadingoftheenamel.The lastfeaturemakesasignificantdifferenceinrelationtoteethof thegenus Liodon Agassiz,1846 (= Leiodon Owen,1841 , non Swainson,1839),whicharesmooth,includingthetypematerial of Leiodon anceps Owen, 1845 from the Upper Campanian Belemnitella mucronata Zone of Essex, England ( Lingham−Soliar 1993).

ThematerialdescribedbyArambourg(1952)isinneedof revision; it may represent a new mosasaurid taxon. Awaiting this revision, we provisionally denote the Polish and Maastrichtspecimensas“ Mosasaurus (Leiodon) cfr. anceps ” sensu Arambourg(1952),tostressapossibleoccurrenceofanallegedly typically African species in Europe.

Plioplatecarpinae sp. A

Fig. 9B.

Material.—Asingle,fragmentarytoothcrownIGPUWAR−5 from the Upper Campanian opoka at Piotrawin.

Description.—As preserved, this bicarinate tooth crown measures38.0mminheight,and20.2mminwidth(atthebase);the cross section is elliptical, with lingual and buccal surfaces of subequalconvexity.Anteriorcarina sharp,welldeveloped,the posterior carina not being preserved; no serrations visible. The crown has a slight posterior recurvature. The buccal surface showsatleastsevenfacetsofunequalwidth,thelingualsurface 9–10;thesefacetsdonotreachmid−height.Veryfaintstriaeon bothsurfacesarevisible;theseareconfinedtotheproximalportion of the crown; otherwise the crown shows smooth enamel. Theupperportionoftoothisbroken;inanteriorview( Fig.9B 2 ), theslightlingualrecurvatureofthecrownmaybeseen.

Discussion.—Incombiningfacettingwithproximalstriaeand slightlingualrecurvatureofthecrown,thepresentspecimenis reminiscent of teeth assigned to the genera Plioplatecarpus Dollo,1882 and Platecarpus Cope,1869 .Itistoopoorlypreserved to allow a more definite taxonomic assignment.

Plioplatecarpinae sp. B

Fig. 9A.

Material.—AsingletoothMKD.MP−18fromtheupperUpper Maastrichtian opoka at Nasiłów.

Description.—As preserved, this bicarinate tooth measures 24 mm in height, and 8.6 mm in width (at the base); in cross section it is elliptical, with subequal lingual and buccal surfaces. Both anteriorand posteriorcarinae are welldeveloped; serrations are preserved in patches only. The crown has a slight posterior and lingual recurvature. The buccal surface shows at least seven facets of comparable width, the lingual surface 11–12; these facets do not reach mid−height. Close to thebase,veryfaintstriaeonbothsurfacesarevisible,confined tothemostproximalportionofthecrown,otherwisesmooth.

Discussion.—In showing a combination of well−developed facetting,aslightlingualrecurvatureofthecrown,andbasal crownstriae,thepresentspecimenisreminiscentofteethassignedtothegenera Plioplatecarpus and Platecarpus .However, it lacks the highly typical, abrupt posterior recurvature from the mid−height of the crowns, as seen in Plioplatecarpus .Moreover, itsfinebasalstriaearenotaspronounced asthosein P. marshi Dollo,1882 (especiallylingually)from theMaastrichtiantypearea(seeDollo1882; Lingham−Soliar 1994a; Kuypers et al. 1998). It should also be noted that some teeth from the Maastrichtian of Zaire described by Lingham−Soliar (1994b) as cf. Mosasaurus lemonnieri , are similar to the present specimen.

In comparison with tooth crowns here assigned to Mosasaurus cf. lemonnieri ( Fig. 7 ), the present tooth is more slen− der,hasmore facetsboth buccally and lingually,and showsa lesserlingualrecurvature.Plioplatecarpinaesp.A.(seeabove) isconsiderablylessslender,isoflargersizeandhasfewerfacets on the lingual surface and no serrations on the carinae.

Figures

Fig.7. Mosasaurus cf. lemonnieri Dollo,1889c,fromtheupperUpperMaastrichtianopokaatNasiłów. A.ZPALR.9/2inlingual(A1),anterior(A2),buccal (A3),andposterior(A4)views. B.ZPALR.9/1inbuccal (B1),posterior(B2),anterior(B3),andlingual(B4)views. C.ZPALR.9/5inobliquebuccalview.

Fig.8.“Mosasaurus (Leiodon)cfr. anceps” sensu Arambourg(1952),fromtheupperUpperMaastrichtianopokaatNasiłów. A.ZPALR.9/3inposterior (A1) and buccal (A2) views. B. ZPAL R. 9/4 in anterior (B1), buccal (B2), posterior (B3), and lingual (B4) views.

Fig.2. Mosasaurus cf. hoffmanni Mantell,1829,fromtheDaniangreensandatNasiłów(redepositedlateLateMaastrichtianmaterial). A.IGPUWAR−1in buccal(A1),lingual(A2),andanterior(A3)views. B.IGPUWAR−2inposterior(B 1)andlingual(B2)views. C.IGPUWAR−3inposterior(C 1),buccal(C2), and anterior (C3) views.