ABSTRACT Fly-speck fungi reproduce via thyriothecia that consist of sporogenous tissue appressed to cuticle surfaces of plant leaves and covered by a shield-like scutellum. Thyriothecial scutella likely evolved repeatedly in Dothideomycetes (Ascomycota), and their morphology varies by lineage. Fly-speck fungi have an exceptionally good fossil record that begins in the Mesozoic. The interpretation of scutellum characters in fossils may provide insights into origins of Dothideomycetes and help calibrate the timing of ascomycete evolution. From sediments of the Lower Cretaceous (125–112 Ma) Potomac Group of Virginia, from Dutch Gap Canal, lower Zone 1, we found scutella similar to those of extant Aulographaceae (Dothideomycetes), attached to a single piece of dispersed coniferous cuticle. We analyze hyphae and scutellum development among four extant Aulographaceae species for comparison with the fossil. The excellent preservation of fungi on the leaf cuticle surface allows us to infer a developmental sequence for the fossil. Scutellum development begins with coordinated growth of multiple neighboring generator hyphae and continues with hyphae producing two-dimensional pseudomonopodial, dichotomous, radial growth. Asci and ascospores were not found. We coded states for seven morphological characters using direct observations of the fossil and eight extant taxa, and using the literature for 28 others. We inferred a phylogeny using nuclear 18S and 28S rDNA of 36 extant taxa, 34 Dothideomycetes and two Arthoniomycetes. The phylogeny includes newly determined sequences from five species, two from Aulographaceae. With a branch-and-bound search, we inferred the most parsimonious placements of the fossil given the molecular tree topology. The parsimony analysis constrained by the rDNA phylogeny places the fossil taxon among stem lineages near Aulographaceae or among the known living members of Aulographaceae. We describe the fossil morphotype as Protographum luttrellii, gen. et sp. nov. The fossil provides the oldest evidence of morphological characters restricted among extant fungi to Aulographaceae.

中文翻译：

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来自弗吉尼亚州早白垩世波托马克群（125-112 Ma）的一种新的叶生蝇斑真菌：Protographum luttrellii，gen。等 sp. 十一月

摘要 蝇斑真菌通过甲状腺鞘膜进行繁殖，甲状腺鞘膜由附着在植物叶片表皮表面并被盾状盾片覆盖的孢子组织组成。Thyriothecial scutella 可能在 Dothideomycetes (Ascomycota) 中反复进化，它们的形态因谱系而异。蝇斑真菌具有从中生代开始的非常好的化石记录。对化石中盾片特征的解释可以提供对 Dothideomycetes 起源的见解，并有助于校准子囊菌进化的时间。从位于 1 区下部荷兰峡运河的弗吉尼亚州下白垩统 (125-112 Ma) 波托马克群的沉积物中，我们发现了与现存的 Aulographaceae (Dothideomycetes) 相似的盾片，附着在一片分散的针叶表皮上。我们分析了四种现存 Alographaceae 物种的菌丝和盾片发育，以与化石进行比较。叶表皮表面真菌的出色保存使我们能够推断出化石的发育序列。盾片发育开始于多个相邻生成菌丝的协调生长，并继续菌丝产生二维伪单足、二分、径向生长。未发现子囊孢子和子囊孢子。我们使用对化石和 8 个现存分类群的直接观察为 7 个形态特征编码状态，并使用其他 28 个分类群的文献。我们使用 36 个现存分类群、34 个 Dothideomycetes 和两个 Arthoniomycetes 的核 18S 和 28S rDNA 推断系统发育。系统发育包括来自五个物种的新确定的序列，其中两个来自 Aulographaceae。通过分支定界搜索，我们推断出给定分子树拓扑结构的化石最简约的位置。受 rDNA 系统发育约束的简约分析将化石分类群置于 Aulographaceae 附近的茎谱系或 Aulographaceae 的已知活成员之间。我们将化石形态描述为 Protographum luttrellii, gen。等 sp. 十一月 该化石提供了现存真菌中仅限于 Aulographaceae 的形态特征的最古老证据。