Proteaceae

Carpenter, Raymond J. & McLoughlin, Stephen, 2025, A new leaf species of Proteaceae and other Gondwanan elements from the early Paleogene Lota-Coronel flora of south-central Chile, Australian Systematic Botany 38 (1), pp. 1-17 : 6-9

Justification for assignment to Proteaceae

A thorough phylogenetic assessment of leaf architecture and venation types across Proteaceae is lacking but we hypothesise that the large, lobed, simple leaf-type of the new species that shows evidence of teeth and semicraspedodromous venation is definitively proteaceous, and is not found in any other taxa, extinct or extant. Circumstantial evidence that this, and other Southern Hemisphere leaf fossils of proteaceous aspect, indeed belong in the family is that Proteaceae pollen is typically diverse and abundant across this region in the Paleogene ( Dettmann and Jarzen 1998). Moreover, many such leaves have well-preserved cuticles (or at least with faithfully recorded diagnostic imprints thereof: Carpenter et al. 2014 a) showing brachyparacytic stomata and compound trichome bases (i.e. an annular surface scar associated with more than one underlying epidermal cell), that in combination provide strong evidence supporting attribution to the family ( Carpenter et al. 2005).

Certain fossil forms of very large lobed leaves from the Northern Hemisphere have historically been assigned to Artocarpus J.R.Forst. & G.Forst. (breadfruits and jackfruits), an extant genus of Moraceae but such leaves are clearly entire-margined and the better-preserved specimens (notably ‘ A.’ lessigiana (Lesq.) Knowlt.) are known to have venation and cuticular morphology that indicates affinities with Lauraceae instead ( Upchurch and Wolfe 1987; K. R. Johnson, pers. comm. to Manchester 2014).

Proteaceaefolia is necessary because we do not regard any previous genus to be a satisfactory repository for the fossils. These cannot be assigned to Euproteaciphyllum G.J.Jord., R.J.Carp. & R.S.Hill because this genus requires cuticular evidence ( Carpenter and Jordan 1997; Jordan et al. 1998). Also, previous genera for impression fossils, many established from the Northern Hemisphere before the late 20th century (e.g. Proteoides Heer ), do not define characters that are strong evidence for Proteaceae , and it is extremely doubtful that any of the specimens assigned to these are proteaceous (e.g. Cookson and Duigan 1950; Johnson and Briggs 1963, 1975; Gonzalez et al. 2007; Olde 2017). Even in the Southern Hemisphere, Carpenter et al. (2016) warned against inferring that all species of Banksieaeformis R.S.Hill & Christophel (erected for Banksia - like leaves lacking cuticle: Hill and Christophel 1988) truly represent Banksia or even Proteaceae .

Comparisons with other fossil taxa and relationships within the family

Lobed and small-toothed leaf species of Proteaceae have been described from other Southern Hemisphere Paleogene assemblages, including the cuticle-bearing

Megahertzia paleoamplexicaulis R.J.Carp. & Rozefelds ( Carpenter and Rozefelds 2023) and Maslinia grevilleoides D. T. Blackburn ( Blackburn 1981) from Eocene strata of southern Australia. The known specimens of these two species are approximately half the size of the Arauco–Concepción type specimen. Moreover, Megahertzia A.S.George & B.Hyland can readily be differentiated by the amplexicaul leaf base and although the gross morphological features of the Chilean fossils could satisfy the diagnosis for Maslinia , the lack of cuticle precludes assignment there. The early Eocene Patagonian Lomatia occidentalis (E. W. Berry) Freng. differs in having imparipinnate or pinnatisect leaves ( Frenguelli 1943; Gonzalez et al. 2007) with much narrower segments.

Extant Proteaceae is well known for the great variety of foliage forms that change in many cases throughout the development of the plant (or in some cases, of the shoot). According to Johnson and Briggs (1975), Flora treatments ( Sleumer 1954, 1955; Virot 1968; Orchard et al. 1995; Prance et al. 2007; Hopkins and Pillon 2020) and personal observations, large pinnately lobed leaves in plants that are older than seedling stage are not found in South America, and are limited to Australasia and Malesia: these occur in subfamilies Persoonioideae ( Placospermum C.T.White & W.D.Francis ) and especially Grevilleoideae ( Alloxylon P.H.Weston & Crisp , Athertonia L.A.S.Johnson & B.G.Briggs , Buckinghamia F.Muell. , Darlingia F.Muell. , Grevillea R.Br. ex Knight , Heliciopsis Sleumer , Orites R.Br. , Megahertzia , Stenocarpus R.Br. and Virotia L.A.S.Johnson & B.G.Briggs ) but are absent in the large subfamily Proteoideae . Adult plants having such leaves with small teeth occur exclusively in tree species of eastern Australian rainforests: i.e. Orites excelsus R.Br. and Megahertzia amplexicaulis of the tribe Roupaleae , and Athertonia diversifolia (C.T.White) L.A.S.Johnson & B.G.Briggs ( Johnson and Briggs 1975) of tribe Macadamieae subtribe Virotiinae .

The true phylogenetic position of Proteaceaefolia araucoensis , presumably within subfamily Grevilleoideae , cannot be inferred in the absence of cuticular evidence. However, we consider that the fossils are morphologically closest to leaves found within Orites excelsus ( Fig. 2 ) and note with relevant significance that: (1) leaf fossils ( O. excelsoides R.J.Carp. & G.J.Jord. ) with cuticle distinctively similar to Orites excelsus occur in the early Oligocene of Tasmania ( Carpenter and Jordan 1997; Carpenter 2012); (2) follicular fruits assigned to Orites ‘without reservations’ ( Gonzalez et al. 2007, p. 254) occur in the early Eocene of Patagonian Argentina. These fruits co-occur with imparipinnately lobed leaves assigned to Lomatia occidentalis but these lack apomorphic support (including cuticular evidence) for referral to that genus and could well belong in other genera ( Carpenter 2012), especially within Orites ; (3) Pole (1994) reported poorly preserved but small-toothed and probably trilobed leaf specimens from the early to middle Eocene of New Zealand that he assigned to ‘cf. Orites excelsa ’; (4) together with O. excelsus , other extant Orites species currently occur in Tasmania, mainland south-eastern Australia and South America, and genetic evidence does not contradict a vicariance explanation for this distribution ( Barker et al. 2007). We rejected the option to attribute the fossils to Orites but the future recovery of better-preserved specimens, especially with cuticular details, may allow this.

Other elements of the NRM Arauco –Concepción collections

A full taxonomic review of other specimens from the Buen Retiro site and others of the Arauco –Concepción Coal Measures is beyond the scope of this study. We briefly discuss and illustrate some specimens but for more information on the occurrence, age and current taxonomic attributions of the Chilean Cenozoic plant fossils in the NRM collections, the reader is directed to the searchable database (see https://samlingar.nrm.se/faces/pages/results.xhtml).

The species previously established from the Chilean assemblages, i.e. Lygodium skottsbergii ( Fig. 3 ), Dacrycarpus chilensis ( Fig. 3 ), Retrophyllum araucoensis ( Fig. 3 ) and Coronelia molinae are all represented in the Buen Retiro collection. Lygodium specimens are abundant, as are numerous sterile foliage specimens labelled as ‘Polypodiopsida’ ( Fig. 3 ) that we confidently refer to Blechnaceae . This foliage is strikingly similar to that of the extant Chilean hard fern, Parablechnum chilense (Kaulf.) Gasper & Salino that intriguingly occurs in the same region of Chile today, but which, on molecular evidence, belongs to a clade that evolved and diversified much more recently than the early Paleogene ( Testo et al. 2022). Sterile fronds of this species have a distinctively undulate margin and the same feature is clearly apparent in many of the fossils ( Fig. 3 ). Engelhardt (1891, pp. 642–644 and pl. 2, fig. 1–4) described apparently similar foliage from Lota as Pteris cousiniona Engelh. , and other Blechnum L.-like foliage is known from the spatially and temporally similar Quinamávida flora ( Troncoso 1992). More recently, Machado et al. (2023) discussed these taxa and other Blechnaceae fossils in light of well-preserved sterile foliage from the Arroyo Chacay flora (of likely early Eocene age) of Argentina described as ‘cf. Parablechnum C.Presl’, also noting strong resemblance to P. chilense and the closely related P. cordatum (Desv.) Gasper & Salino.

Angiosperm leaves and especially leaf fragments are common. The specimens of Proteaceaefolia araucoensis and several other fragments of likely Proteaceae leaves have been observed only from Buen Retiro – S160375 and S160390 appear to be parts of toothed, pinnatisect leaves with organic remains ( Fig. 3 ) that are not assigned to P. araucoensis due to insufficient diagnostic features. Nevertheless, UV fluorescence yielded evidence at least of stomata with brachyparacytic subsidiary cells on S160375, the arrangement that is typical of Proteaceae . Leaves of likely several species of Lauraceae ( Fig. 3 , 4 ) occur throughout. These are of uncertain affinities but include at least one taxon with suprabasally actinodromous venation ( Fig. 3 ). Cunoniaceaelike and Elaeocarpaceae-like specimens include those from Buen Retiro (S160421-01) that are accompanied by a label with the determination ‘ Caldcluvia cf. paniculata ’ by O.H. Selling in 1942 ( Fig. 4 ). We agree with this determination based on overall leaf morphology, including the nature of the craspedodromous venation and the cunonioid teeth. A few leaves with intramarginal veins and the type of highangled secondaries typical of Myrtaceae were observed from Buen Retiro ( Fig. 4 ). Similar foliage occurs at Peumo ( Fig. 4 ). Some leaves were identified by Selling as comparable with Sterculiaceae and we especially note a lobed, basally actinodromous leaf ( Fig. 5 ) as reasonably belonging to Malvales . Perhaps the most striking fossil described by Engelhardt (1891, p. 645, pl. 1, fig. 1) is Sabal ochseniusi Engelh. , a section of palmate, deeply folded palm foliage from Curanilahue in which the presence of a costa may be interpreted. A further Curanilahue specimen, missing any evidence of a costa, was collected by Dusén in 1896 ( Fig. 5 ) and Berry (1922, p. 91) noted another from Concepción. Various other foliage types are present, including evidence of compound leaves and leaf specimens with apical ‘driptips’ ( Fig. 5 ).

As discussed by Wilf et al. (2014), a specimen assigned to Zamia L. by Engelhardt (1891) from Coronel is evidently lost but could represent a monocot. Several incomplete Buen Retiro specimens also possess parallel venation consistent with monocot affinities ( Fig. 5 ).

Figures

Fig. 2. (a, b) Proteaceaefolia araucoensis specimens from Buen Retiro. (c) A leaf of the very similar extant Australian species Orites excelsus. (a) S165435 (Type specimen). Minute teeth are generally indistinct, however the inset magnification from region x of the apical lobe is interpreted to show a tooth right of t, to which a minor vein below b branches from a secondary vein loop l. (b) S160367. Note the vein loops and branches to minute teeth along the margin on the right. (c) Specimen from Beechmont, Queensland, Australia. Note especially the same form of lobing and marginal teeth as in the fossils. Scale bars: 5 cm for (a) and (c); 1 cm for (b). The scale intervals for (a) inset are 1 mm.

Fig. 3. (Caption on next page)

Fig. 4. Examples of Lota–Coronel fossils collected by Halle from Buen Retiro (b–d, f, g) and Minas Cantarana Site 1 (a) and Dusén from Peumo (e, h). (a) S160606 likely Lauraceae. (b, c) cf. Caldcluvia paniculata (Cunoniaceae). These specimens and others occur on the same rock, suggesting that these are leaflets originating from a compound leaf. (b) S160421-01-04, (c) S160421-01-01. (d) Original label accompanying (b, c). (e) S160016 incomplete Elaeocarpaceae-like or Cunoniaceae-like leaf. (f) S160527-0203 Elaeocarpaceae-like or Cunoniaceae-like leaf. (g, h) Likely Myrtaceae; (g) S160523-01, (h) S160014. Scale bars: 1 cm.

Fig. 5. (Caption on next page)